To provide a magneto-resistance effect film which has high sensitivity and reduced temperature dependency, to provide a magnetic sensor using the same, and to provide a rotation angle detecting device.

A spin valve giant magneto-resistance effect film having a fixed layer having unidirectional magnetic anisotropy, a free layer whose magnetization direction rotates toward an external magnetic field, an intermediate layer sandwiched between the fixed layer and free layer, and a protective layer formed on the free layer, is characterized in that the fixed layer, intermediate layer, free layer, and protective layer are formed in this order on a base body, the fixed layer includes a first ferromagnetic layer of CoFe alloy and a second ferromagnetic layer of CoFe alloy, and a first nonmagnetic layer coupling the magnetization directions of the two ferromagnetic layers in antiparallel, and the two ferromagnetic layers of the fixed layer are equal in magnetization-film thickness product and the protective layer is a second nonmagnetic layer formed principally of Ru.