PURPOSE: To effectively heat a heating medium for using in steaming, frying, etc., by using a heater in which a communication path is provided in the peripheral side and bottom of a heating tank housed with a heating medium, and alos a heating pipe is horizontally provided inside the heating tank.

CONSTITUTION: Communication paths 1 and 2 are provided in the periheral side and bottom of a heating tank 4 with a heating medium 5, and a heating pipe 6 whose one end is connected to a burner 9 and the other end is connected through the communication paths 1 and 2 to a draft fan 15, is horizontally provided inside the heating tank 4. A heating gas enters through a nozzle 10 into the heating pipe 6 to heat the heating medium 5 and further circulates through the communication paths 1 and 2 to heat the heating medium inside. During the period, the radiation of heat to the outside can be prevented, and the efficiency of heating can therefore be enhanced.