PURPOSE: To achieve a energy-saving and to obtain a fuel cost-saving effect, by changing the heat source of a sauna heater from an electric power to a gas fuel.

CONSTITUTION: The air for combustion is sucked by a blower 21, a secondary air flows in a blast pipe 6 through a secondary air inlet 22, and flows in a combustion chamber 5 after it turns by 90°. Meanwhile, a primary air flows in a mixing pipe 20 through a primary air port 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 burner port 24 through a 90° bent part to start combustion. A combustion gas heats a tubular combustion chamber 5, and heat rays consisting of mainly infrared rays are radiated from the outer surface of the pipe to 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 pipe, infrared rays are radiated from the outer surface of the flue 25, and the combustion gas, flowing in a zigzag manner through the flue 25, is exhausted through a chimney 27 from the blower 21 to the outdoors.