TOKYO, JULY 29 -- An appeals court today upheld former prime minister Kakuei Tanaka's conviction and four-year prison sentence on charges of taking bribes from Lockheed Corp.

The Tokyo high court also upheld the $3.2 million fine a lower court had levied against the ailing, 69-year-old former leader. That was the amount of the payoff Tanaka was accused of receiving from the U.S. aircraft maker in postwar Japan's most serious political scandal.

Opposition parties demanded that Tanaka, who has been free on bail, resign his seat in parliament.

Tanaka's lawyer told reporters Tanaka would appeal to the Supreme Court.

The ruling came almost four years after a lower court found Tanaka, his secretary and three former executives of Marubeni Corp., the trading house that acted as Lockheed's agent, guilty of graft, perjury and other charges.

Neither Tanaka, who is recuperating from a severe stroke in 1985 that has left him paralyzed, nor the other defendants attended today's court session.

Tanaka became prime minister in 1972. He was forced to resign a year later following a financial scandal unrelated to the Lockheed affair. The Lockheed scandal broke in February 1976, when testimony in a U.S. congressional hearing disclosed that Lockheed had spent about $12 million to promote the sale of its aircraft in Japan.