PURPOSE: To provide a simple apparatus capable of utilizing solar heat efficiently, by arranging metal reflector plates stepwise on a heat insulating layer covered over the roof surface, and disposing a transparent plate over the metal reflctor plates with a proper spacing to the same.

CONSTITUTION: On a heat insulating layer 2 applied over the surface of roof 3, there are arranged stepwise metal reflector plate 1 having a heat absorbing pipe 4 extended along the length of each horizontal portion 1a. Over the reflector plates 1, a transparent plate 10 is disposed with a proper spacing to the same. With such an arrangement, the sunlight passed through the transparent plate 10 strikes the reflector plates 1 and is reflected thereby, with the solar heat being absorbed by the pipes 4. Here, since the heat insulating layer 2 is provided under the reflector plates 1, releasing of solar heat absorbed by the pipes 4 can be prevented and convection and dispersion of solar heat is prevented by the function of transparent plate 10. Thus, it is enabled to absorb solar heat and reflect the sunlight efficiently by the function of reflector plates 1, to heat water in the pipes 4 and to feed hot water to a hot-water storing tank 8 or to a hot-water supplying section (not shown).