If the answer above is None it means there is no specific mention in the legislation, but you still need to ask local law enforcement before drinking in Taiwan.
Parents, guardians, and others taking care of people under 18 shall not supply alcohol to them or risk administrative fines of 10000 to 50000 new Taiwan dollars (Art 55). No person shall supply alcohol to anyone under the age of 18 (Art 91).
You can find more legal details and links here:
Wikipedia Legal Drinking Page