A shock sensor detects shocks from all directions in a plane. A shock-sensing member extends longitudinally and is housed in a case. The shock-sensing member is rotatably supported by a supporting pin at an off-center point in terms of mass of the shock-sensing member. The shock-sensing member has a magnet mounted on each of two diametrically opposing ends of the shock-sensing member. Each magnet opposes a magnetoresistive effect element fixed in the case. The magnetoresistive effect element may include four elements electrically connected in a bridge configuration. When the shock-sensing member receives a shock, the shock-sensing member rotates about the supporting member causing the magnetoresistive effect element to be subjected to a change in the magnetic field of the magnet. The output of the magnetoresistance changes with changes in the magnetic field and is processed by an output circuit which in turn outputs a sensor output accordingly.