There is provided a magnetic detecting element having a large .DELTA.RA. A free magnetic layer has a three layer structure in which a CoFe layer, an Ni.sub.aFe.sub.b alloy layer (where a and b are represented by at %, 0.ltoreq.a.ltoreq.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 .beta. increases, and the product .DELTA.RA of the resistance variation of the magnetic detecting element and the area of the element can be made increased.