A transmission includes a gear ratio change mechanism, a driving circuit and an electronic control unit (ECU). The gear ratio change mechanism has a motor for continuously varying the gear ratio. The driving circuit applies a pulse voltage to the motor. The ECU outputs a control signal to the driving circuit. The duty ratio and/or the pulse height of the pulse voltage is changed according to the control signal. The ECU performs a low-pass filtering process on the control signal to output the low-pass filtered control signal to the driving circuit. Gear ratio change shocks are thereby suppressed.