PURPOSE: To efficiently conduct space heating with fresh air within respective rooms and to make the structure of the device compact by forming a hot air generating unit provided with a heat exchange part, a heating part and a pressure chamber, and connecting the pressure chamber to respective hot air blow off ports by means of a duct.

CONSTITUTION: A hot air flow generator 4 comprising a heat exchange part 1 for heat-exchanging fresh air supplied from the external part with exhaust air to be exhausted from the inside of the room to the external part, and a pressure chamber 3 into which fresh air warmed at the heating part 2 is introduced, is formed, and the outlet port 5 of the pressure chamber 3 is connected to respective hot air flow ejecting ports 6 by means of a duct 7. That is, external fresh air is exchanged with exhaust air exhausted from the room to the external part, and further air is heated at the heating part 2 to have a required temperature. Then, air is supplied to the pressure chamber 3 so as to blow off hot air through the hot air blow off ports 6. The duct 7 opens the hot air blow off ports 6 at the ceiling, floor, wall and the like, and hot air is directly injected into the room from the hot air blow off ports 6.