Chiang Fu-chung was convicted of leaking large amounts of confidential documents to China through his uncle, a Taiwanese businessman based on the mainland, the high court said.
No other details were released but he can appeal the ruling.
Chiang, who worked for the air force radar command and control centre, has been detained since his arrest last year.
Taiwanese media have reported that the Chinese military has long sought access to the centre, which houses highly sensitive information including details on the air force's "Strong Net" radar programme and the US-made Patriot surface-to-air missile system.
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Taiwan has been hit by a string of spying scandals in recent years.
In September a retired vice admiral was jailed for 14 months for collecting confidential military information for China.
An ex-air force lieutenant colonel in February received 12 life sentences for passing military secrets to China during a period of six years for a reported payment of USD 269,000.
In 2011 an army general and chief of an intelligence unit was sentenced to life for spying for China in one of the island's worst espionage scandals.
Although they split in 1949 at the end of a civil war, Beijing still regards the island as part of its territory awaiting reunification, by force if necessary.