PURPOSE: To obtain an inexpensive current sensor capable of being massproduced and excellent in capacity by forming the sensor from a high permeability material containing fine pieces of a ferromagnetic material and a resin binder mutually fixing the fine pieces to form a specific shape.

CONSTITUTION: Fine pieces 2 of a ferromagnetic material are mutually fixed using a resin as a binder and molded into a specific shape to form a magnetic circuit 1 composed of a high permeability material containing org. matter. The compositional ratio of the fine pieces 2 and the resin binder can be determined corresponding to the characteristics of an objective sensor and, when high permeability is required, the ratio of the fine pieces 2 is increased. The magnetic circuit 1 is produced so as to have a doughnut shape, a square shape or other free shape. A gap 3 is formed to a part of the magnetic circuit 1 and, by expanding the gap 3 by applying the elasticity of the magnetic circuit 1, a Hall element 4 is inserted in the gap 3 as an magnetic sensor. In order to concentrate magnetic flux to the inserting and fixing part of the Hall element 4 to enhance current detection capacity, the magnetic circuit part near to the insertion part is pref. made fine.