Antonio Chiang -- a veteran journalist and political commentator -- said he had drunk whisky and wine over dinner with friends before he was caught late on August 2, local media reported.
His arrest triggered calls for his resignation from campaigners in Taiwan against drink-driving.
The office of Taiwan's new president Tsai Ing-wen said today she had accepted his resignation and "respected" his decision.
Taipei prosecutors handed Chiang a suspended indictment and a Tw USD 60,000 fine yesterday, according to Taiwan's Central News Agency.
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Taiwan's legal limit is 0.25 mg per litre.
Campaign group Taiwan Against Drunk Driving -- headed by a mother whose daughter was killed by a drunk driver -- last week protested outside the foreign ministry, calling Chiang a "disgrace" to the island.
Chiang told Central News Agency today he feels "very guilty and remorseful" for causing trouble for the government.
Taipei maintains representative offices instead of embassies as it does not have formal diplomatic relations with many nations, which instead choose to recognise rival Beijing.
Chiang writes a column for Taiwan's Apple Daily newspaper, which often publishes articles critical of China.