PURPOSE: To provide a hot-water mat type floor heating device, in which water will never be spilt in the case of removing a hot-water mat out of a heat source machine.

CONSTITUTION: A floor heating device is constituted of a mat 2, accommodating a hot-water circulating passage 1, and a heat source machine 4, to which the mat 2 is connected detachably through a communicating hose 3. In the heat source machine 4 of the floor heating device, in which a water tank 5, a sending side pipeline 9, connected to a coupling socket 8 through a water tank 5, a pump 6 and a heat exchanger 7, and a returning side pipeline 19 from the coupling socket 8 to the water tank 5 are provided, a first branched pipeline 12, branched from an intermediate point between the heat exchanger 7 and the heat exchanger 8 of the sending side pipeline 9 through a first three-way valve 11 is joined with the water tank 5. At the same time, a second branched pipeline 14, branched from the pipeline 10 through a second three-way valve 13, is joined with an intermediate point between the water tank 5 and the pump 6 of the sending side pipeline 9 and, further, a solenoid valve 15 is interposed between the water tank 5 and the joining point to receive water in the mat 2 into the water tank 5 by the pump 6 through both of three-way valves 11, 13 and branch pipes 12, 14 upon water extracting operation.