A copper-based alloy excellent in dezincing resistance comprises, in percentage by weight, Cu: 57-69%, Sn: 0.3-3%, Si: 0.02-1.5%, Bi: 0.5-3%, and Pb: not more than 0.2%, where the ratio of Si/Sn expressed in weight percentage is in the range of 0.05-1 and apparent zinc content as defined by the following formula is in the range of more than 39-50 wt. %, and the balance of unavoidable impurities: Apparent Zn content=[(Zn %+2.0Sn %+10.0Si %)/(Cu %+Zn %+2.0Sn %+10.0Si %)]100. Despite the fact that contains no added environment-unfriendly Pb, the alloy exhibits enhanced cuttability, together with excellent forgeability, dezincing resistance and hot forgeability.