A magnetic sensor includes a substrate, and a magneto-resistive element portion which is provided on the substrate and has a predetermined magneto-sensitive direction, and in which a bias magnetic field is applied in a direction orthogonal or substantially orthogonal to the magneto-sensitive direction. The magneto-resistive element portion includes a magnetic layer having a negative magneto-striction constant, and stress-induced anisotropy of the magnetic layer develops in a direction parallel or substantially parallel to the direction of the bias magnetic field in response to a tensile stress act on the substrate in a direction parallel or substantially parallel to the magneto-sensitive direction.