PURPOSE: To utilize heated gas as a heat source by a method wherein the solar heat is collected by confronting a heat collecting board of breathable porous body to the solar ray, and gas is passed through towards the opposed side of the heat collecting board which confronts to the solar ray, heat exchanged in the heat collecting board.

CONSTITUTION: The solar heat is collected by confronting the heat collecting board 1 of breathable porous body, which is made of the continuous foam resin foaming body or the interlacing body of organic or inorganic fibers, and at the same time gas is passed through towards the opposite side of the heat collecting board 1 which confronts to the solar ray, and heat exchanged in the heat collecting board 1, and heated gas is utilized as a heat source. As a result, the heat loss of the solar heat from the heat collecting board is remarkably reduced in every respect on radiation, convection and conduction, and the heat collecting efficiency is highten and the installation cost is kept low and the apparatus is controlled easy.