PURPOSE: To obtain a simple manufacture of the solar energy collector, at low cost by a method wherein a number of transparent ribs are formed radially on the outer periphery of a solar energy collecting cylinder colored in a dark color of the black system, made of a synthetic resin and having an inner passage and a transparent and light transmitting outer cylinder is provided.

CONSTITUTION: The solar energy collecting cylinder 2 is made of a synthetic resin, colored very darkly in a dark color of the black system and formed with a passage for flowing water or other heat medium therethrough. Thus constructed solar energy collecting cylinder 2 is prominent in the heat collecting characteristic. On the outer periphery of the cylinder 2, there are provided a number of radial ribs 3 of a transparent and light transmittent synthetic resin such as acrylic resin. The light transmittent outer cylinder 4 made of the same material as the ribs 3 is formed over the tip ends of the ribs 3 for define a number of heat insulative spaces 7. These parts allotted with reference numerals 2 to 4 are molded integrally by the extrusion molding technique to construct the solar energy collector A. A plurality of thus constructed collectors A are arraged in parallel, with the upper and lower ends connected in communication with a heat collecting pipe 6 and a water supply pipe 5, thereby constituting the solar energy collector/hot water suplly device in combination.