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 Ethiopia.
It is prohibited for any person to sell, offer, serve or allow to serve alcohol beverages in substantial quantities to any infant or young person. The criminal code defines a young person as any person under the age of 15 years. But the Criminal Code Proclamation 414 (2004) states: Whoever endangers the health of another, intentionally and unscrupulously, by administering or serving, or by causing or permitting to be administered or served, to minors (defined as anyone under the age of 18 years) (...) alcohol beverages or spirituous liquors of such kind or in such quantity as to make their injurious effect certain or probable, is punishable with simple imprisonment not exceeding one year, and fine. The Revised Family Code Proclamation No. 213 (2000) Article 215 defines a minor as anyone who has not attained the full age of 18.
You can find more legal details and links here:
Wikipedia Legal Drinking Page