To supply a current not to be oscillated to a squib for start by reducing oscillations caused by wiring inductance in simple configuration.

The output terminal of an amplifier 20 for constant current control is connected through a resistor 20 to the gates of MOSFET 16 and 17. Since it can be regarded from the physical structure of the MOSFET a capacitor exists between the gate and the drain, the output terminal of the amplifier 20 is connected through the serially connected resistor 21 and capacitor to a power source 11. These resistor 21 and capacitor reduce the oscillations of a voltage on the side of the power source 11 caused by the inductance of wiring 13. As a result, a constant current not to be oscillated can flow to a squib 14.