An acceleration sensor includes a housing member, a spring member attached to the housing member, a magnetic field generation member fixed to the housing member, and at least one magnetic field detection sensor and a weight member, fixed to the spring member so that the at least one magnetic field detection sensor faces the magnetic field generation member. The spring member has freedom in at least one direction of acceleration to be detected. The at least one magnetic field detection sensor is provided with at least one multi-layered MR element including a magnetization fixed layer and a magnetization free layer. A magnetic field is applied to the at least one multi-layered MR element from the magnetic field generation member in a direction substantially perpendicular to a lamination plane of the at least one multi-layered MR element when no acceleration is applied. When an acceleration is applied, the magnetic field is applied to the at least one multi-layered MR element from the magnetic field generation member in a direction changed by an angle corresponding to the applied acceleration from the substantially perpendicular direction.