To provide a magnetoresistance effect device that can securely reduce the so-called Barkhausen noise.

The opposite surface of an upper shield layer 35 is prescribed nearly along one plane 51. The upper shield layer 35 faces a magnetic domain control film 42, an electrode film 43, and a magnetoresistance effect film 41. It is expected that residual magnetization Mr will exist in the same direction as magnetization Mg of the magnetic domain control film 42 in the upper shield layer 35, after the magnetic domain control film 42 is polarized. On the surface opposite to the upper shield layer 35, the magnetization Mr cannot easily break off. A magnetic pole cannot be easily generated. Weakening in a vertical bias magnetic field BS can be avoided based on the residual magnetization Mr of the upper shield layer 35.