A fastener for bags includes an engaging piece (12) fixed on a lid (11) side of a bag and a latch mechanism (19) fixed on a main body (13) side of the bag and adapted to admit the engaging piece detachably. Since part of the engaging piece is clad with a member (15) for preventing infliction of injury, the lid in the process of being opened or closed has no possibility of inflicting any injury on a metallic surface (28) disposed on the latch mechanism side. Thus, the metallic surface can always be kept beautiful.