The crash sensor of the present invention comprises a magnet, a sensing mass made of a ferromagnetic material and attractable by the magnet, a sleeve made of a paramagnetic material and restricting the movement of the sensing mass in one direction, a pair of strips that make a closed circuit by contact with the sensing mass having moved in one direction and a body fitted with the magnet and housing the sensing mass, the sleeve and the contacts; the crash sensor further comprising a magnetic shield made of a ferromagnetic material and covering the magnet and the body. The magnetic shield forms a closed-type magnetic field by covering the magnet and the body and forms an appropriate magnetic loop in the vicinity of the sensing mass, so that the crash sensor also acts as a magnetic shield to protect itself from being influenced by outside ferromagnetic bodies and makes effective use of the magnetic force of the magnet. The above pair of strips are fitted in the same direction vertically on the inner wall of the body, whereby they do not project out in the axial direction so that the crash sensor can be of a reduced whole length, as well as of smaller outside diameter than conventional crash sensor with its contacts positioned facing each other.