PURPOSE: To thoroughly remove the frost formed around a suction pipe by a method wherein a ceramic heater is used in a defrosting heating body and the resistance density of the ceramic heater is made different in the axial direction.

CONSTITUTION: Thermally sprayed metal electrodes 4 are formed at both ends of a ceramic heater 2 of an electrically conductive ceramic sintered body consisting mainly of silicon carbide and a lead wire 5 is connected through such electrodes. At this time, the surface of a connecting part 5a of the ceramic heater 2, the thermally sprayed metal electrodes 4 and the lead wire 5 are covered with an electric insulating layer 3. The heater thus formed is inserted and retained in a silicone cap. The ceramic heater 2 is formed in such a way that its wall thickness varies in the longitudinal direction or its resistance density is different in the axial direction according to the sintering conditions and the earth-moving conditions. Also, the ceramic heater 2 is made with a cylindrical, flat or starry cross section to permit a sufficient area to be formed so as to support a deodorizing catalyst and adsorbing agent for the deodorizing purposes.