PURPOSE: To improve the rate of operation, to facilitate the temperature control under cooling and to improve heat-efficiency, by placing an outer heat-insulation layer on an inner heat-insulation layer of the furnace main body interposing a space therebetween and supplying air to the space in cooling.

CONSTITUTION: A formed ceramic material in a casing 24 on a furnace floor 15 verti cally movable with a lifter is heated and baked with a heater 22. In the course of raising the temperature and maintaining at a high temperature, three heat-insulation layers comprising an inner heat-insulation layer 12, an air layer in a space 14 and an outer heat-insulation layer 13 are inclined to get an energy-saving furnace having decreased heat-dissipation loss. In the cooling stage after the completion of the stage for keeping at a high temperature, air is supplied to the space 14 with a blower 21 through an air-supplying pipe 18 and blasted into the space 14 through an air-blasting port of the air-supplying pipe 18. The air heated by dissipated heat is collected in an upper air-exhaustion pipe 19 and discharged through an exhaust duct to outer atmosphere. The temperature-lowering operation time can be shortened by this process without causing the increase in the temperature of a room containing the ceramic baking furnace and, accordingly, the operation rate of the baking furnace can be improved.