PURPOSE: To prevent responsiveness of speed change control from being influenced by a tension control pressure and to prevent generation of a slip of a transmission belt, by providing a tension control pressure change moderating means which moderates a change in a direction of decreasing tension of the transmission belt under tension control pressure.

CONSTITUTION: Since a change in a direction of decreasing tension of a transmission belt of the second line oil pressure Pl2, which is a tension control pressure corresponding to a tension control pressure change moderating means, is moderated, responsiveness of speed change control is improved from being influenced by the tension control pressure. Further in the case of governing the second line oil pressure Pl2, a change in a direction of increasing tension of the transmission belt is not moderated, so that a slip of the transmission belt is prevented from being generated, despite providing a means corresponding to the tension control pressure change moderating means, by permitting increase of the second line oil pressure Pl2 relating to rapid increase of input torque.