FORM 6-K

SECURITIES AND EXCHANGE COMMISSION

Report of Foreign Private Issuer

Pursuant to Rule 13a-16 or 15d-16
of the Securities Exchange Act of 1934

For the month of July, 2004

Commission File Number 1-7616

PIONEER CORPORATION
(Translation of registrant’s name into English)

4-1, MEGURO 1-CHOME, MEGURO-KU, TOKYO 153-8654, JAPAN
(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F:

Form 20-F þ                    Form 40-F o

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):                              

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):                              

Indicate by check mark whether by furnishing the information contained in this Form, the registrant is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes o                    No þ

If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): 82-

Table of Contents

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

This report on Form 6-K contains the following:

For Immediate Release
July 28, 2004

Pioneer Announces First-Quarter Results for Fiscal 2005

TOKYO — Pioneer Corporation today announced its consolidated first-quarter business results for the period ended June 30, 2004.

Consolidated Financial Highlights

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Consolidated Business Results
For the first quarter of fiscal 2005, ended June 30, 2004, consolidated operating revenue was ¥163,487 million (US$1,513.8 million), a 7.2% increase over the corresponding period in the previous year. For the same period, operating income was ¥5,004 million (US$46.3 million), a 34.8% decrease, and net income decreased by 49.1% to ¥1,497 million (US$13.9 million). The average value of the yen was up 7.9% against the U.S. dollar and up 1.8% against the euro from the corresponding period in the previous year.

Home Electronics sales increased 1.7% from the corresponding period in the previous year to ¥51,967 million (US$481.2 million). In Japan, sales decreased by 12.6% to ¥13,855 million (US$128.3 million), due to a decline in sales of recordable DVD drives for personal computers and audio products, despite the sales increase of DVD recorders and home-use plasma displays. Overseas sales increased 8.2% to ¥38,112 million (US$352.9 million), due to rises in sales of home-use plasma displays and DVD recorders worldwide, despite a decline in sales of DVD players and audio products worldwide, as well as digital cable TV set-top boxes in North America.

Car Electronics sales amounted to ¥79,555 million (US$736.6 million), up 6.4% over the corresponding period in the previous year. In Japan, sales increased 3.1% to ¥32,331 million (US$299.4 million). This resulted from continuous strong sales of car navigation systems to automobile manufacturers, despite the decreased sales in consumer markets of both car navigation systems, due to new model switches in this quarter later than in the corresponding quarter of the previous fiscal year, and car audio products. Overseas sales increased 8.8% to ¥47,224 million (US$437.3 million), due to growth in sales of car navigation systems in North America and Europe as well as higher sales of car audio products in other regions.

Royalty revenue from Patent Licensing decreased 15.9% from the corresponding period in the previous year to ¥2,875 million (US$26.6 million). This reflects the expiration of the Company’s optical disc-related patents in certain areas.

Others sales increased 25.2% from the corresponding period in the previous year to ¥29,090 million (US$269.4 million). In Japan, sales decreased 2.5% to ¥12,653 million (US$117.2 million) reflecting a shift in sales to China of semiconductors related to laser pickups and lower sales of business-use plasma displays, despite the increase in sales of factory-automation systems. Overseas, sales were up 60.2% to ¥16,437 million (US$152.2 million), due to increased sales of optical disc manufacturing systems in Asia and semiconductors related to laser pickups in China, despite the decrease in sales of business-use plasma displays.

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Operating income decreased 34.8% from the corresponding period of the previous year to ¥5,004 million (US$46.3 million). This was despite increased net sales, and reflected a decrease in gross profit margin due to intensified competition and adverse effects of the stronger yen against major currencies. Net income came to ¥1,497 million (US$13.9 million), a 49.1% decrease from the corresponding period of last year, due to a decrease of operating income.

Basic net income per share of common stock was ¥8.53 (US$0.08), compared with ¥16.75 for the corresponding period in the previous year. Diluted net income per share was ¥7.46 (US$0.07), compared with ¥16.75 for the corresponding period in the previous year.

Cash Flows
Cash flows from operating activities decreased by ¥11,981 million to ¥5,676 million (US$52.6 million) net cash used, compared with ¥6,305 million net cash provided in the corresponding period of the previous year. This decrease is mainly attributable to increased operating capital requirement, resulting from increases in inventories and payments for income taxes and employee bonuses. Net cash used in investing activities was ¥13,283 million (US$123.0 million), up by ¥2,645 million compared with ¥10,638 million cash used in the corresponding period last year, mainly due to an increase in capital expenditures.

Business Forecasts for Fiscal 2005
Our consolidated business forecasts for fiscal 2005, ending March 31, 2005, are unchanged from those announced on April 27, 2004, which are shown below. We assume average yen-U.S. dollar and yen-euro exchange rates for the remaining period of fiscal 2005 of ¥105 and ¥130, respectively.

Cautionary Statement with Respect to Forward-Looking Statements
Statements made in this release with respect to our current plans, estimates, strategies and beliefs, and other statements that are not historical facts are forward-looking statements about our future performance. These statements are based on management’s assumptions and beliefs in light of the information currently available to it. We caution that a number of important risks and uncertainties could cause actual results to differ materially from those discussed in the forward-looking statements, and therefore you should not place undue reliance on them. You also should not believe that it is our obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise. We disclaim any

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such obligation. Risks and uncertainties that might affect us include, but are not limited to, (i) general economic conditions in our markets, particularly levels of consumer spending; (ii) exchange rates, particularly between the yen and the U.S. dollar, euro, and other currencies in which we make significant sales or in which our assets and liabilities are denominated; (iii) our ability to continue to design and develop and win acceptance of our products and services, which are offered in highly competitive markets characterized by continual new product introductions, rapid developments in technology and subjective and changing consumer preferences; (iv) our ability to successfully implement our business strategies; (v) our ability to compete and develop and implement successful sales and distribution strategies in light of technological developments in and affecting our businesses; (vi) our continued ability to devote sufficient resources to research and development, and capital expenditure; (vii) our ability to continuously enhance our brand image; (viii) the success of our joint ventures and alliances; and (ix) the outcome of contingencies.

Pioneer Corporation is one of the leading manufacturers of consumer- and business-use electronics products such as audio, video and car electronics on a global scale. Its shares are traded on the New York Stock Exchange (ticker symbol PIO), Euronext Amsterdam, Tokyo Stock Exchange, and Osaka Securities Exchange.

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The U.S. dollar amounts in this release represent translation of Japanese yen, for convenience only, at the rate of ¥108=US$1.00, the approximate rate prevailing on June 30, 2004.

Attached are consolidated financial statements.

For further information, please contact:
Investor Relations Department, Corporate Communications Division
Pioneer Corporation, Tokyo
Phone: +81-3-3495-6774 / Fax: +81-3-3495-4301
E-mail: pioneer_ir@post.pioneer.co.jp
Website: http://www.pioneer.co.jp/corp/ir/index-e.html

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Pioneer Corporation and Subsidiaries

CONSOLIDATED FINANCIAL STATEMENTS OF PIONEER CORPORATION

(1) OPERATING REVENUE BY SEGMENT

(In millions of yen)

(2) CONSOLIDATED STATEMENTS OF INCOME

(In millions of yen)

Pioneer Corporation and Subsidiaries

(3) CONSOLIDATED BALANCE SHEETS

(In millions of yen)

Pioneer Corporation and Subsidiaries

(4) CONSOLIDATED STATEMENTS OF CASH FLOWS

(In millions of yen)

Pioneer Corporation and Subsidiaries

(5) SEGMENT INFORMATION

The following segment information is prepared pursuant to the regulations under the Securities and Exchange Law of Japan.

<Business Segments>

(In millions of yen)

Notes: