An accelerometer for measuring the displacement of a magnet body using magnetic detecting elements is provided, the accelerometer having superior measurement accuracy by suppressing influence of an external magnetic field such as the earth magnetic field. The accelerometer has detecting units each having a cantilever which is elastically deformed so as to rotate around a fixed end thereof, a magnet body provided at a free end of the cantilever, and a magnetic detecting head portion disposed outside the rotation region of the cantilever. In order to correct detection signals output from the magnetic detecting head portions, the accelerometer has peripheral magnetic field detecting portions for measuring an external magnetic field acting on the magnetic detecting head portions and the magnet body for correcting a detection signal output from the magnetic detecting head portion. The correction includes a correction of the cantilever movement in response to the external magnetic field. The beam may be formed of a Ni-P alloy, and its support may extend parallel to the beam, to protect the beam.