To make a controller compact, to simplify the same and to reduce the loss by charging a capacitor for driving an electromagnetic valve in reserve, and timely dispersing the load of a booster circuit by boosting the voltage for the shortage when necessary.

A power supply transistor to a solenoid 10 is divided into two, that is a transistor 12 for attraction driving and a transistor 403 for retaining driving, and an emitter of the transistor 403 is not a booster circuit 3 but a battery 2. The application of the reverse voltage to the transistor 403 is prevented by a diode 404 when the transistor 12 is switched on in the attracting. The charging condition of a capacitor 11 is checked at a specific period, and the capacitor 11 is charged to a desired voltage when it is judged that the charging is necessary. By periodically charging the capacitor in reserve, the output of the booster circuit 3 can be inhibited in each charging, and the operation of high efficiency is available by the booster circuit of small output.