To dispense with piping between a charge pump and selector valves as well as to constitute the charge pump provided on a hydraulic transmission (HST) on a oil pressure source in relation to the selector valves for controlling a hydraulic actuator arranged outside the HST.

In this HST, a hydraulic motor M is hydraulically connected to a hydraulic pump P to be driven by a power input shaft through a closed circuit, a charge pump 34 to be driven by a power input shaft 3 is provided on a housing for housing the hydraulic pump P and the hydraulic motor M, and oil in the housing is supplied to the closed circuit. Selector valves 36, 37 for controlling a hydraulic actuator arranged outside the HST are housed in a case 6 for housing the charge pump 34, oil discharged from the charge pump 34 is partially introduced to the selector valves 36, 31 through an oil passage formed in the case, oil is supplied to the hydraulic actuator, and return oil from the hydraulic actuator is recirculated to the housing.