A magnetostrictive torque sensor includes first and second magnetostrictive films mounted on a pinion shaft and having different magnetic anisotropic properties, a first detecting coil disposed in facing relation to the first magnetostrictive film, a second detecting coil disposed in facing relation to the second magnetostrictive film, a transistor, and a detector for detecting a torque applied to the pinion shaft based on a first detected signal representative of a potential at the junction between the first detecting coil and the second detecting coil.