An object is to be able to accurately discriminate an object of a collision. A device has a collision detection to which are connected a pressure sensor that detects pressure within a pressure chamber, and a vehicle speed sensor that detects vehicle speed, and the collision detection determines effective mass of a collided object on the basis of an integrated value obtained by integrating, at a predetermined sectional integration width, detection results of the pressure sensor, and a converted vehicle speed signal obtained by subtracting a predetermined value α from a vehicle speed signal of the vehicle speed sensor by using a predetermined vehicle speed converting map or the like. Then, when the determined effective mass exceeds a predetermined threshold value, the collided object is discriminated as a pedestrian.