A planar pressure-sensitive switch unit has multiple pressure-sensitive switches that are disposed in a longitudinal direction of a bumper cover of a vehicle with given intervals for detecting the number of collision objects. Collision load sensors are disposed between a bumper reinforcement and side members for detecting a total collision load by adding up two outputs. Then, a collision load per a single collision object is computed by dividing the total collision load by the number of collision objects and is compared with a collision load corresponding to a pedestrian. Thus, even when the vehicle collides with multiple objects at the same time, collision with a pedestrian can be properly determined.