A planar heating element for a window includes a resin base having a flat or curved surface, a heating element formed of a conductive sheet having a uniform specific resistance and provided to spread in the form of a planar shape along the shape of the surface of the resin base, and conductive current supply portions provided to extend in the form of bands on opposite ends of the heating element, so as to allow a current to pass through the heating element. The heating element has a locally increased specific resistance portion whose specific resistance locally increases when a current is passed through the heating element from the current supply portions.