To provide a snap fastener, the male and female snap members can be easily engaged, and having improved stability during engagement.

The snap fastener is composed of a male snap member (1) made of a synthetic resin and a female snap member (4) made of a synthetic resin. The synthetic resin male snap member (1) has an engaging protrusion (12) protruded from a male substrate (11). The engaging protrusion (12) is made up of a neck (13) and a head (14). The head (14) has an engaging edge (15) formed. The female snap member (4) has a female substrate (41) having an engaging hole (43) which has the head (14) of the engaging protrusion (12) elastically deformed for passing through and a head storage chamber 44 to store the head (14) having passed through. The engaging protrusion (12) is provided, eccentrically from the center of the male substrate (11). The head storage chamber (44) is provided with an engaging protrusion (45) in face contact with the engaging edge.