A pressure sensor, which detects a pressure in a space close to an inner side of an exterior member of a vehicle, and an occupant protecting device, which protects an occupant inside a vehicle are provided. An electronic control unit determines an occurrence of collision in the case where the pressure and a change per unit time of the pressure each satisfy a collision condition, and then makes the occupant protecting device operate. At this time, the collision condition is set to restrict the determination indicative of an occurrence of collision unless the change per unit time of the pressure is larger with lowering the pressure.