Bumper collision sensor

A bumper collision sensor can detect collision without hurting a pedestrian even if a bumper is deformed significantly. The bumper collision sensor includes a wire, a tension sensor, and a substrate. The wire has an extendable portion in a part thereof. The tension sensor is connected to one end of the wire. The substrate is mounted with the tension sensor and the wire and is attached, with plasticity, to the bumper. The tension sensor is fixed to one end of the substrate. The wire is arranged in the tension sensor along a longitudinal direction of the substrate with a stress equal to or lower than a value set in advance. The other end of the wire is fixed to the substrate.