When a pinned magnetic layer includes an underlayer and a Heusler alloy layer, a product ΔR×A of the amount of change in resistance and an element surface area of a magnetic sensor per unit area is increased. That is, a magnetic field detection sensitivity of the magnetic sensor can be improved. It is believed that the magnetic field detection sensitivity of the magnetic sensor is improved by the present invention because a misfit percentage between the underlayer and the Heusler alloy layer is small, and therefore the crystallinity or the periodicity of the Heusler alloy layer is improved.