An acceleration sensor includes a housing member (20, 20), a spring member (21, 61, 71) attached to the housing member, the spring member having freedom in at least one direction of acceleration to be detected, a weight and magnetic field generation member (22, 62) fixed to the spring member, and at least one magnetic field detection sensor (23, 24, 63) attached to the housing member to face the weight and magnetic field generation member. The at least one magnetic field detection sensor (23a, 24a, 63a) is provided with at least one multi-layered MR element including a magnetization fixed layer and a magnetization free layer. A direction of magnetic field applied to the at least one multi-layered MR element from the weight and magnetic field generation member is perpendicular to a lamination plane of the at least one multi-layered MR element when no acceleration is applied.