PURPOSE: To melt snow automatically by receiving a detecting output detecting snow by a snow sensor while operating a circulating pump forwarding a heating medium to a heat-transfer tube when the temperature of the thermal medium in a liquid storage tank s higher than the temperature of thawing.

CONSTITUTION: When the temperature sensor T1 of a solar heat collector 2 detects a temperature sufficient for heating the thermal medium of a heat storage tank 3, a controller S drives a heat-collecting pump P2, and the thermal medium of the liquid storage tank 3 is heated. When a snow sensor T2 detects the specified quantity of snow coverage and the temperature of the thermal medium of the liquid storage tank 3 is the temperature of thawing, 0°C, or higher, a circulating pump P1 is driven. The thermal medium is forwarded to a heat-transfer tube 4 through an on-off valve VD and a changeover valve VC1, and a road surface L is heated. The heating medium passed through the heat-transfer tube 4 is passed through a conduit A2, and returned to the return port 3d of the liquid storage tank 3.