A magnetostrictive sensor capable of obtaining both enhanced productivity and reduced variations in outputs can be obtained. A torque sensor includes a substrate and a plating film disposed on the outer peripheral surface of the substrate. The substrate includes a plating portion, masking portions, and tilt portions and. An outer peripheral surface of the plating portion is a surface parallel to a shaft center of the substrate in a side cross-sectional view. Outer peripheral surfaces of the tilt portions are slopes tilted relative to the shaft center in the side cross-sectional view. The plating film is formed on a plating surface and slopes in such a manner that end portions in the axial direction are located on the slopes. The plating film on the slopes has a thickness smaller than the thickness of the plating film on the plating surface.