The same rotation torque is input to a continuously variable transmission of a vehicle which continuously varies a speed change ratio and a reduction gear unit. A planetary gear mechanism is provided comprising an output shaft which varies a rotation direction according to a relation between the output speed of the continuously variable transmission and the output speed of the reduction gear unit. The continuously variable transmission varies the speed change ratio according to an oil pressure balance between two oil chambers. A direction change-over valve selectively supplies a first oil pressure and a second oil pressure to these oil chambers, and a control valve controls a differential pressure of the first oil pressure and second oil pressure. The control range of the differential pressure controlled by the control valve is narrowed due to reversal of the oil pressure supply direction by the direction change-over valve according to whether the vehicle is moving forward or in reverse, and control precision is thereby improved.