PURPOSE: To provide an indirect heating system which can be installed by an easy method, has a heating capability, requires less facility expense and maintenance cost and can be used in a wide range of application.

CONSTITUTION: The room temperature is detected by a room temperature sensor 10 mounted in a heated room 9. A heater 7 having a high specific heat is mounted in a hollow within a high air-tight high thermal insulating heated room 3 composed of a reflector plate 4, a heat-resistant thermal insulating plate 5 and a reflecting thermal insulating plate 6 so as to enable circulation heating under a temperature control.