PURPOSE: To implement a scale of a short-wave length, by arranging ferromagnetic element pieces having anisotropic effect of magnetoresistance in correspondence with magnetic grids, and connecting two constituent elements, which are linked by current paths in series.

CONSTITUTION: Detecting element pieces 7 comprising a ferromagnetic bodies having anisotropic effect of magnetoresistance are formed at an interval that is half the wavelenfth of λ of a magnetic grid 9. The element pieces 7 are connected by current paths 10. Current terminals (a) and (c) and an output terminal (b) are provided in a detecting element 8 such as this. The element 8 faces a magnetic grid surface 9 of a magnetic scale. By the same way, a detecting element 8' is arranged at a specified interval, and a magnetic scale is formed. In this way the magnetic scale of a short wave length can be formed. Thus the accurate detection can be performed by a simple detecting circuit.