To restrict a biting property of an output side rotary member against a brake cam and facilitate releasing of their bit state.

This brake device 100 comprises an outer ring 10, brake cams 20, and output side rotary member 30 arranged inside each of the brake cams 20 and having abutting parts 51A that can be abutted against an inner surface 23 of each of the brake cams 20, and this brake device is constituted such that a rotating operation inputted to the brake cams 20 is transmitted to the output side rotary member 30 through the abutting parts 51A and in turn the rotating operation in at least one direction of the output side rotary member 30 is not transmitted to the brake cams 20 by pushing the brake cams 20 against an inner peripheral surface 11A by the abutting parts 51A. The brake device 100 has tension coil springs 60 of which one end is engaged with the brake cams 20, the other end is engaged with the output side rotary member 30 so as to cause the output side rotary member 30 to bias it in a rotating direction opposite to one direction against the brake cams.