To save power consumption while eliminating uneven temperature of a floor surface.

A radiation plate 9 comprising an aluminum plate or a copper plate is arranged on a radiation pipe 1a which has an inner tube with a heater cable 6 inserted thereinto, an outer tube 12 enclosing the inner tube 11 and a heat accumulation body 13 sealed into a hollow layer between the outer tube 12 and the inner tube 11 and on heat accumulation pipes 2a and 3a which have heat accumulation bodies 23 and 33 sealed into hollow tubes 22 and 32 parallel arranged contacting one or both sides of the radiation pipe 1a in such a manner that the undersurface thereof contacts the pipes. The top surface of the radiation plate 9 is kept in contact with the undersurface of a floor plate 8.