<p>A vehicle speed calculating section calculates the vehicle velocity by integration of a forward and reverse acceleration of a vehicle. A first deforming speed calculating section calculates a first deforming speed by integration of acceleration from a first acceleration sensor. A second deforming speed calculating section calculates a second deforming speed by integration of acceleration from a second acceleration sensor. A first deforming speed correcting section subtracts a vehicle speed from the first deforming speed and outputs it to a determining section. A second deforming speed correcting section subtracts the vehicle speed from the second deforming speed and outputs it to the determining section. In the determining section, the collision object determination is made on the basis of the corrected deforming speed.</p>
