A diagnosis apparatus for an airbag system includes a squib, a driving transistor connected in series with the squib to activate the squib by driving current when driven by a control circuit. The control circuit drives the driving transistor to supply small monitoring current periodically to the squib under slew rate control. As a result, a change rate of rise and fall of each monitoring current is reduced to about 0.1 mA/.mu.s or less thereby reducing radio noise.