PURPOSE: To reduce production of noises in a heating chamber and to prevent contamination of the air in the heating chamber and the occurrence of oxygen deficiency, by constituting an infrared rays radiating device such that a burner and a blower for combustion air are installed outside the heating chamber.

CONSTITUTION: The air for combustion is sucked by a blower 21 and a secondary air, flowing in a blast pipe 6 through a secondary air inlet 22, flow in a combustion chamber 5 after it turns by 90°. Meanwhile, a primary air flows in a mixing pipe 20 through a primary air inlet 23 with the aid of the suction force of the blower 21, and as the primary air is mixed with a fuel gas flowing in through a nozzle 19, it flows out of a flame port 24 through a 90° bent part to start combustion. A combustion gas heats a tubular combustion chamber 5 which radiates heat rays consisting mainly of infrared rays from the outer surface of the pipe, and the heat rays heat a person in a room. A combustion gas, flowing out of the combustion chamber 5, enters a flue 25 to heat the inside of the tube, infrared rays are radiated from the outer surface of the flue 25, and the combustion gas, passing in a zigzag manner through the flue 25, is exhausted through a chimney 27 from the blower 21 to the outdoors.