To provide an inexpensive device which can control a shift actuator within a wide hydraulic pressure range with accuracy and facility.

A select actuator 16 is an operated member which makes a select fork be shifted to each sift stage through a neutral position. A shift actuator 15 is an operated member which operates a shift fork through the select fork. A flow control means 12 drives the select actuator by controlling the flow rate of hydraulic fluid discharged from a hydraulic pressure source. Hydraulic differencial pressure generation means 10, 11 are operated for introducing the operation liquid discharged from the hydraulic pressure source while so controlling that the hydraulic pressures in both pressure chambers 15A, 15B of the shift actuator 15 are specified values. Double action of the shift actuator 15 is thus performed by the hydraulic pressure difference between the pressure chambers. The operation hydraulic pressure can be varied from the low to high values without applying high pressure to one of the pressure chambers. The shift actuator can easily be controlled.