To save energy by enabling changeover of the heating area of a floor heating panel using hot water.

A floor heating panel 4 is provided with hot water pipes 5 and 6 of two systems dividing the heating area thereof in two, while a selector valve 3 switching over a flow of hot water is provided between a forward pipe 2 of the hot water connected to a heat source unit 1 producing the hot water and the inlets of the hot water pipes 5 and 6 of two systems provided for the floor heating panel 4. Moreover, a Y branch pipe 7 is connected between the outlets of the hot water pipes 5 and 6 and a return pipe 8 connected to the heat source unit 1. The heating area is changed over by operating the selector valve 3 in this constitution.