PURPOSE: To accurately detect a signal so as not to generate the erroneous operation due to noise or the unexpected application of a magnetic field in a magnetic sensor detecting a change of magnetic force.

CONSTITUTION: In a magnetic sensor of integrated hybrid constitution formed so that a magnetoresistance element 12 is mounted on an aluminum substrate 11 to which pattern printing is applied and a detection circuit composed of an IC chip taking in the magnetic signal detected by the magnetoresistance element 12 to convert the same to digitalized electric signal is mounted on the substrate, a bias magnet 17 is mounted on the substrate 1 in the magnetic field sensing direction of the magnetoresistance element 12 and circuit processing is performed so that the magnetic field sensing capacity of the magnetic sensor is always set in the same direction and switching operation is generated to a magnetic field stronger than the magnetic field generated from the bias magnet 17.