[PURPOSE]According to the invention there is provided a magneto-resistive effect element having a larger magneto-resistive ratio than in the prior art.[SOLUTION MEANS]The magneto-resistive effect element (10) of the invention has a compound semiconductor layer (11) composed of a compound semiconductor such as InAs, metal layers (12A and 12B) composed of a metal element such as Ni not composing the compound semiconductor, and interlayers (13A and 13B) of NiInAs or the like composed of the constituent elements of the compound semiconductor and a metal element, situated between the compound semiconductor layer and the metal layer. In the magneto-resistive effect element (10) of the invention, application of a magnetic field (50) alters the conductance with respect to the electric current (60) flowing through the metal layer (12B), interlayer (13B), compound semiconductor layer (11), interlayer (13A) and metal layer (12A).