A plurality of clutch hydraulic pressure gradual increase patterns for maintaining jerk value at a level of a target value are previously determined in dependence on vehicle weight and speed stages; a clutch hydraulic pressure gradual increase pattern corresponding to the vehicle weight and speed stage selected at the time of speed change is selected from the aforesaid plurality of clutch hydraulic pressure gradual increases patterns. Then, hydraulic pressure in a speed change clutch to be engaged is caused to increase gradually in accordance with the thus selected clutch hydraulic pressure gradual increase pattern.At the time point when a speed change command is issued, a speed change clutch to be subsequently brought in the engaged state is fed with hydraulic oil and gradually increasing hydraulic pressure is exerted on the speed change clutch after the time point when termination of filling time is confirmed with respect to this speed change clutch. Further, at this time point hydraulic pressure in the speed change clutch which is now brought in the engaged state decreased.