To make it possible to reduce in size the geomagnetic bearing sensor by previously giving magnetic anisotropy to a ferromagnetic core, and improving the applying efficiency of the geomagnetism of the core, thereby maintaining the bearing accuracy high.

Ferromagnetic cores K (K1 to K4) are formed on a flattened layer. Magnetic anisotropy of the same direction as the direction of a magnetic field induced in the core K by the input of geomagnetism is given to the respective cores K. Since the anisotropy is previously given, it is not necessary to align the directions of the fields in the cores K to the same direction. Therefore, the applied efficiency of the geomagnetism of the cores K is improved. The saturated magnetic fields of the respective cores K are reduced, and the driving power can be reduced. Accordingly, the size can be reduced with high accuracy, and the geomagnetism is efficiently supplied as a magnetic signal to the MR sensor (magnetoresistance effect element) to obtain the high bearing accuracy.