To prevent a carpet from floating at the time of passing hot water by burying a resin pipe for passing hot water in a groove made in the upper surface of a foamed resin mat, applying an aluminum foil and a carpet onto the upper surface thereof and applying the aluminum foil also onto the lower surface of the foamed resin mat.

A hot water mat A is manufactured by burying a flexible hot water resin pipe 3 in a zigzag groove 2 made in the upper surface of a foamed resin mat 1 and applying an aluminum foil 4 onto the upper surface thereof. The hot water mat A is laid on the upper surface of an underlying floor material 8 and a carpet 6 is laid thereon. An aluminum foil 7 is also applied to the lower surface of time foamed resin mat 1. When hot water is conducted through the hot water mat A, temperature of the hot water resin pipe 3 increases and the pipe 3 elongates to cause elongation of the foamed resin mat 1. But elongation is blocked by each aluminum foil 4, 7 and the hot water mat A is prevented from being warped.