A shift actuator disposed outside a power unit that is easily positioned in the neutral position during mounting. A motorcycle equipped with a shift actuator includes a transmission; a shift shaft for changing the gears of the transmission; and a crankcase that covers the shift shaft and the transmission. The shift actuator includes a motor; an output shaft connected to the shift shaft with a connecting device therebetween; a worm gear interposed between the motor and the output shaft; a case supporting the motor, the output shaft, and the worm gear; and a potentiometer supported by the case and sensing the position of the output shaft. The worm gear transfers a driving force from the motor to the output shaft but transfers no driving force from the output shaft to the motor.