A snap button functioning as both a male snap element and a female snap element which are not required to be exactly positioned to each other when engaged with each other. Two engaging projections (20) and two engaging recesses (30) are circumferentially alternately arranged on a button body (10) of the snap button (1). Radially inwardly projecting projections (26, 26') are formed at the front ends of the engaging projections (20), and radially outwardly projecting projection locking sections (36, 36') are formed at radially inner portions of a recess opening (31). The engaging projections (20) are each shaped such that a horizontal cross-section of the engaging projection (20) gradually decreases in the direction in which the engaging projection (20) project. Also, the circumferential area of the engaging recesses (30) is set greater than the circumferential area of the engaging projections (20). Chamfered sections (36a) are provided at radially inner portions of the recess opening (31). The outer peripheral surfaces (33) of the engaging recesses (30) are tilted upward and radially outward.