Abstract: A heat radiating pipe (2) that is disposed in a hot water mat (1) is extended from the hot water mat (1) to provide an extended portion that is used as connecting pipes (2a and 2b) to a heat source machine (11). The construction makes it possible to prevent a water leak as there is no connection therebetween, and reduces costs for parts and installation as no connection tool, such as a coupler, is used. Further, guide pieces (13 and 14) attached with cover members (17) are arranged at positions where the connecting pipes (2a and 2b) are extended, and the connecting pipes (2a and 2b) are disposed by using the guide pieces (13 and 14), so as to efficiently utilize heat radiated from the connecting pipes (2a and 2b), and to prevent thermal loss.