PURPOSE: To prevent an uncomfortable cold air flow from flowing through foots upon floor heating by forming an air flow passage with lower side of a heating source, and further forming an inlet in a floor in the vicinity of a wall surface for connecting between the inside of a room and the air flow passage.

CONSTITUTION: A floor surface member 1 is heated by an electric heater 2 disposed under a floor. A downward stream produced from a window surface 4 at a low temperature typically brings about a room air flow such as indicated by A. However, provided there are disposed an air air flow passage 7 below the heater 2, an inlet 5 for the downward stream below the window surface 4, and an outlet 4 for the downward stream on the opposite side to the inside of the room the downward stream A is induced from the inlet 5 to the air flow passage 7, and heated with the heater 2, and further returned from the downward stream outlet 6 into the room. Thus, air circulating in the room eliminates any uncomfortable feeling.