There is provided a magnetic detecting element having a large ΔRA. A free magnetic layer has a three layer structure in which a CoFe layer, an NiaFeb alloy layer (where a and b are represented by at %, 0≦a≦25, and a+b=100), and a CoFe layer are laminated from the bottom. If the at % of Ni in an NiFe alloy that exists in the free magnetic layer is in this range, a spin-dependent bulk scattering coefficient β increases, and the product ΔRA of the resistance variation of the magnetic detecting element and the area of the element can be made increased.