A solenoid supply current value is predicted from a detected battery voltage, an operational fluid temperature, and the like, and a chopper ON time during chopping drive is reduced, and relatively, a chopper OFF time is increased by using, for example, a voltage correction coefficient which becomes smaller as the battery voltage becomes larger, or a temperature correction coefficient which is set smaller as the operational fluid temperature is smaller. Alternatively, an overexciting current of the solenoid is detected at least at two time points during overexcitation, and a termination time point of the overexcitation at which the overexciting current reaches a target overexciting current is predicted from the overexciting current value, and the overexcitation is terminated when the termination time point is reached.