There are provided a magnetic detecting element capable of maintaining large .DELTA.RA and of reducing magnetostriction by improving a material forming a free magnetic layer, and a method of manufacturing the same. An NiFeX alloy layer is formed in a free magnetic layer. For example, the element X is Cu. The NiFeX alloy layer formed in the free magnetic layer makes it possible to maintain large .DELTA.RA and to more reduce the magnetostriction of the free magnetic layer, compared with a structure in which an NiFe alloy layer is formed in the free magnetic layer.