PURPOSE: To obtain at low cost the titled heat collecting plate which is easy of processing by a method wherein a metallic panel including, as integral parts the reof, a bottom plate having a plurality of grooves at suitable intervals and opposing side walls formed on both sides thereof is provided, a solar heat adsorbing film is formed on the upper surface of the metallic panel and water pipes are arranged under the bottom plate of the metallic panel.

CONSTITUTION: In case the metallic panel laid on the roof is formed of a band shaped metallic material rolled to have the bottom plate 2 provided with the spaced apart grooves 1 and the opposing side walls 3 and 4 on both sides, thereof, the solar heat adsorbing films are formed on the upper surfaces of the bottom plate 2 and the opposing surfaces of the side walls, respectively. In this case, an engaging section 6 having a draining groove 8 is provided on top of one of the side walls while a receiving section 7 for receiving therein the like engaging section of another metallic panel to be arranged adjacent thereto is provided on top of the other side wall so that a plurality of such metallic panels are connected to one another in sequence.