A clasp (3) having a first member (3A,8A) and a second member (3B,8B) that are respectively disposed to two coupled members (11,12), the clasp being closed by the first member (3A,8A) and the second member (3B,8B) mutually engaging when the coupled members slide in relatively opposite directions. The first member (3A,8A) has a first attachment member (20,80) that has a side wall (21,81) disposed on both sides of a direction intersecting the direction in which one of the coupled members slides, and a spine (22) that connects the side walls, and a button unit (30,90) that has a push button (321) which is urged to the outside from the inside of the coupled members in the direction intersecting the sliding direction of the coupled members, and which is disposed with the one coupled member held between the first attachment member and the button unit. The second member (3B,8B) has a second attachment member (40,100) that has a side wall (41,101) attached at a prescribed position to the other coupled member on both sides of a direction intersecting the direction in which the other coupled member slides. The first attachment member (3A,8A) and the button unit (30,90) are attached at a prescribed position to the one coupled member. The button unit (30,90) has a protruding catch (322) that moves in conjunction with the push button (321) and engages the side walls of the second attachment member when the coupled members are slid together. The side walls of the second attachment (3B,8B) member have a recessed strike (412) to which the protruding catch (322) is inserted from the inside of the side walls.