"The Chinese cyberwar units have been engaging with Taiwan units almost every day, with some severe attacks every few months," Simon Chang said during an interview with the UFO radio network.
"Many of the attacks were aimed at stealing relevant information for use in negotiations with Taiwan," he said.
Zhang Zhijun, director of China's Taiwan Affairs Office, met his counterpart on the island in June despite vocal opposition from Taiwanese people suspicious of closer ties with Beijing.
Zhang holds ministerial status and was the most senior official to fly over from the mainland since the beginning of Communist rule in China, when the two sides parted.
Chang said the Taiwanese military had set up its own cyber units but that they were outnumbered by China's online forces.
Taiwanese government websites have frequently suffered digital bombardments from China, usually during disputes between the two sides, military authorities say.
Ties between Taiwan and China have improved markedly since 2008 when President Ma Ying-jeou of the China-friendly Kuomintang party came to power on a platform of beefing up trade and tourism links. He was re-elected in 2012.
In June 2010 Taiwan and China signed the landmark Economic Cooperation Framework Agreement, a pact widely characterised as the boldest step yet towards reconciliation.
Yet Beijing has still refused to renounce its use of force against the island, which it regards as part of its territory even though Taiwan has ruled itself for more than six decades since their split in 1949 at the end of a civil war.
The United States, a key ally of Taiwan, routinely accuses China of cyber attacks and spying. Five Chinese military officers were indicted for hacking into US companies in May.
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