PURPOSE: To prevent breakage of road surface due to frost heaving, and improve durability by changing over supply of heat reserved hot water or antifreezing solution after heat exchanging to a heat pipe embedded on the road surface or a heating pipe in the road bed, according to snowfall condition or road bed temperature.

CONSTITUTION: A heat pipe 5 connected with a first water feed branch pipe 4 is in the road surface 1, a heating pipe 7 connected with a second water feed branch pipe 6 and a road bed temperature detector 8 connected to a snowfall detector 9 are in the road bed 3, respectively provided. The first water feed branch pipe 4 and the second water feed branch pipe 6 are branched off from a water feed main pipe 12 through a water supply control valve 11. A signal is output from the snowfall detector 9 to an automatic operation board according to snowfall condition or outside air temperature to actuate a pump, the supply water control valve 11 is changed over, hot water or antifreezing solution after heat exchanging is supplied to the first water feed branch pipe 4 to heat the road surface at snowfall, and in case of road bed temperature under 0°C at no snowfall, to the second water feed branch pipe 6 to heat the road bed.