A heater includes a heat generation element which includes a heater wire which spreads in a planar manner, and a metal plate serving as a heat dissipation element which includes a material having a high thermal conductivity, which is placed on a vehicle windowpane side of the heat generation element, which is heated by heat from the heat generation element, and which irradiates heat to the vehicle windowpane side. The vehicle windowpane is heated by the heat irradiated from the metal plate serving as the heat dissipation element.