This clutch actuator includes a hydraulic pressure generating mechanism (51) configured to operate a clutch (26) to provide a connected state or a disconnected state, a motor (52) configured to generate a rotary driving force for driving the hydraulic pressure generating mechanism (51) to a driving shaft (52a), a transmission mechanism (54) configured to transmit the rotary driving force generated in the driving shaft (52a) of the motor (52) to a driven member (54b) parallel to the driving shaft (52a) in an axial direction and disposed coaxially with a cylinder main body (51a), and a conversion mechanism (55) configured to convert the rotary driving force transmitted to the driven member (54b) into a reciprocal driving force of a piston (51b) in a stroke direction, wherein the hydraulic pressure generating mechanism (51), the motor (52), the transmission mechanism (54) and the conversion mechanism (55) are integrated as a unit.