To provide a clutch/brake of a machine press which can improve the cooling performance by positively introducing the air into an outer circumferential surface side of a case member to promote the heat radiation to the outside from the outer circumferential surface of the case member.

A plurality of blades 70 are provided on the other end on the outer side of the case member 6 in the axial direction, the air outside the other end of the case member 6 in the axial direction is positively introduced in the outer circumferential surface side of the case member 6, and a plurality of fins 75 are provided on an outer surface of the case member 6 to further promote the introduction of the air into the outer circumferential surface side of the case member 6.