The power dissipation in the material inductively heated by coils having various shapes was calculated : Heating effect at depth is improved 1) when the radius of the coil is large, 2) when the height of the coil is enlarged, 3) when the coil is placed away from the body, 4) with use of a cylindrical coil rather than a pancake-type coil which has the same radius as the cylindrical one, and 5) by revolving the coil around the central axis rather than by scanning uniformly over the same region. It is impossible to reduce the absorbed power at all points on the entire surface of the material, even if the electric currents in the coils are driven in opposite directions in order to offset the induced current at the surface of the material.