A Hall device of the present invention includes a cross-shaped magnetometric sensing surface, a pair of power terminal portions and a pair of output terminal portions. The surface is formed of a rectangular and mutually opposed extensions provided on each side of the rectangular. The pair of power terminal portions is provided on a pair of the opposed extensions at the surface. The pair of output terminal portions is provided on another pair of the opposed extensions at the surface. Slits extending in each opposed direction completely split the power portions and the output portions and in partway split each extension at the surface, and each of the slits is provided with a separation layer of an insulator. An outline formed of the surface, the power portions and the output portions is quadrature-symmetrical with the center. The Hall device of this structure is highly sensitive to a magnetic field.