A change-speed system for a utility vehicle includes a gear change-speed device operated for change speed in response to an operation of an actuator, a hydraulic clutch for selectively engaging/disengaging power transmission to the gear change-speed device, a current-controlled valve mechanism for feeding pressure oil to the hydraulic clutch and a hydraulic clutch controlling portion for controlling oil pressure in the hydraulic clutch by controlling a value of electric current to the valve mechanism. The hydraulic clutch controlling portion is operable to initiate a disengaging process of the hydraulic clutch based on initiation of the operation of the actuator and operable also to initiate an engaging process of the hydraulic clutch based on completion of the operation of the actuator. The engaging process of the hydraulic clutch includes a first engaging sub-process for rapidly raising the oil pressure to the hydraulic clutch for a predetermined period and a second engaging sub-process for gradually raising the oil pressure to the hydraulic clutch which has been temporarily dropped subsequent to the first sub-process. There is provided a manual setting device for adjusting the value of the electric current to the valve mechanism from the hydraulic clutch controlling portion in the second engaging sub-process.