PURPOSE: To prevent change in color of a tatami mat or a rise of a floor panel due to a temperature rise of the surface of floor without increasing noise of a device by a method wherein lower louvers are slightly inclined with respect to the horizontal direction and upper louvers have inclinations larger that those of the lower ones.

CONSTITUTION: Six louvers 17a are disposed in a vertical direction and upper two louvers 17a out of them each have an inclination larger than that of each of the lower four louvers 17a. Indoor air taken in by a convection fan 14 and heat led upwards by a combustion furnace 13 are mixed together in an air passage 15 after the indoor air has passed above the furnace 13. As a result, hot air having lower temperature is delivered downwards (toward a floor) from the upper two louvers 17a and hot air having higher temperature is delivered nearly in the horizontal direction from the lower louvers to perform heating in a room. Consequently, temperatures near the surface of the floor becomes higher as a whole. And hence, the hot air is prevented from flowing upwards and a heating condition is obtained, wherein high temperature zones are distributed near the surface of the floor.