To provide an impact sensor capable of eliminating the need of a power supply for operation, holding impact record without requiring the power supply, and electrically detecting the record.

An elastic hinge 4 connected between a frame 2 and a mass part 3 is brought in the state of being bent in the longitudinal direction, and the mass part 3 is buckled so as to be deviated upward or downward relative to the position of the frame 2. Also, an electrode 5 is formed on a base 1. When the sensor receives an impact and the mass part 3 is displaced upward, the mass part 3 is held at a new position by the buckling of the hinge 4. The presence or absence of the impact is stored as the position of the mass part 3. The presence or absence of the impact can be detected by detecting a variation in capacitance between the mass part 3 and the electrode 5 due to the positional change of the mass part 3.