A passenger protecting device of a motor vehicle includes an acceleration sensor which issues an acceleration signal representative of the degree of a vehicle collision; a signal processing circuit which, by processing the acceleration signal, issues an ignition trigger signal when judging that the vehicle collision is critical; a DC power source for charging a plurality of back-up capacitors; a plurality of squibs each having first and second terminals, the first terminals of the squibs being connected to a common terminal and the second terminals of the squibs being connected to the back-up capacitors through respective connection lines; a first switch circuit having one terminal connected to the common terminal and the other terminal grounded; and a plurality of second switch circuits, each being disposed in each of the respective connection lines, each second switch circuit being turned ON when receiving the ignition trigger signal from the signal processing circuit. According to the invention, each of the second switch circuits comprises a current limiting means by which a current supplied from each of the back-up capacitors to the corresponding squib is limited.