A clutch unit, comprising: a) an input-side clutch section provided on an input side, for controlling transmission and interruption of a rotational torque to be input; and b) an output-side clutch section provided on an output side, for transmitting the rotational torque from the input-side clutch section to the output side, and interrupting a rotational torque to be reversely input from the output side, c) the output-side clutch section comprising: - an input member to which the rotational torque is to be input; - a stationary member (23, 33, 24, 25) restricted in rotation; - an output member from which the rotational torque is to be output; - an engagement element (27, 37) arranged between the stationary member (23, 33, 24, 25) and the output member, for interrupting the rotational torque from the output member through engagement between the stationary member (23, 33, 24, 25) and the output member, and transmitting the rotational torque from the input member through disengagement between the stationary member (23, 33, 24, 25) and the output member; characterized in that d) the output-side clutch section further comprises control means for engaging, at the time of interrupting the rotational torque, the engagement element (27, 37) between the stationary member (23, 33, 24, 25) and the output member through meshing of projection and depression portions (23a, 27a, 33a, 37a), and disengaging, at the time of transmitting the rotational torque, the engagement element between the stationary member (32, 33, 24, 25) and the output member through unmeshing of the projection and depression portions (23a, 27a, 33a, 37a). a) an input-side clutch section provided on an input side, for controlling transmission and interruption of a rotational torque to be input; and b) an output-side clutch section provided on an output side, for transmitting the rotational torque from the input-side clutch section to the output side, and interrupting a rotational torque to be reversely input from the output side, c) the output-side clutch section comprising: - an input member to which the rotational torque is to be input; - a stationary member (23, 33, 24, 25) restricted in rotation; - an output member from which the rotational torque is to be output; - an engagement element (27, 37) arranged between the stationary member (23, 33, 24, 25) and the output member, for interrupting the rotational torque from the output member through engagement between the stationary member (23, 33, 24, 25) and the output member, and transmitting the rotational torque from the input member through disengagement between the stationary member (23, 33, 24, 25) and the output member; characterized in that - an input member to which the rotational torque is to be input; - a stationary member (23, 33, 24, 25) restricted in rotation; - an output member from which the rotational torque is to be output; - an engagement element (27, 37) arranged between the stationary member (23, 33, 24, 25) and the output member, for interrupting the rotational torque from the output member through engagement between the stationary member (23, 33, 24, 25) and the output member, and transmitting the rotational torque from the input member through disengagement between the stationary member (23, 33, 24, 25) and the output member; d) the output-side clutch section further comprises control means for engaging, at the time of interrupting the rotational torque, the engagement element (27, 37) between the stationary member (23, 33, 24, 25) and the output member through meshing of projection and depression portions (23a, 27a, 33a, 37a), and disengaging, at the time of transmitting the rotational torque, the engagement element between the stationary member (32, 33, 24, 25) and the output member through unmeshing of the projection and depression portions (23a, 27a, 33a, 37a).