To provide a clutch-brake device which can prevent any foreign matters from being bitten in an air cylinder to tighten a clutch mechanism and improve the durability of a lining.

In the clutch-brake device 1 comprising the clutch mechanism 5 to transmit the rotational force of a body member 3 to a driven member, a brake mechanism 6 to brake the rotation of the body member 3, and a switching mechanism 7 which switches the clutch mechanism 5 and the brake mechanism 6 in an interlocking manner, the switching mechanism 7 has the air cylinder 40 to tighten the clutch mechanism 5, the body member 3 has an annular end wall member 11 to close one end side of an air operation chamber 44 of the air cylinder 40, an annular cylindrical part 43a is formed on an air piston member 43 of the air cylinder 40, and the annular cylindrical part 43a is externally fitted to the annular end wall member 11 in an airtight and slidable manner to reliably operate the clutch mechanism 5 and the brake mechanism 6.