A resistor is provided between an exciting coil and the ground, and a diode is provided between a point p1 and a point p2. An exciting current flows on the ground side via the diode until a relay contact is closed immediately after a switch is turned on. Thus, a voltage applied to the exciting coil becomes almost same as a power supply voltage, the relay contact can be surely closed. Further, when the relay contact is closed, since the exciting current flows on the ground side via the resistor the voltage applied to the exiting coil reduces and hence the heat generation amount can be reduced.