PURPOSE: To reduce the loss of heat radiation and to enable the titled heat collector to keep a high heat collecting efficiency even in the case of high temperature heat collection by a method wherein a condensing lens having a focussing point on a heat collecting pipe is provided on the light receiving surface of a transparent vacuum tube and a selective heat absrobing film is formed on the surface of the heat collecting pipe on which the solar rays are irradiated.

CONSTITUTION: The vacuum tube 6 which is made of glass includes a lens section 7 integrally formed therewith and the heat collecting pipe 8 through which a heat medium 1 flows is sealed axially within the vacuum tube 6. Further, the selective heat absorbing film 9 is formed on the surface of the heat collecting pipe 8 by an almite processing or the like. With the above structure, since the focussing point of the lens section 7 of the vacuum tube 6 lies on the surface of the heat collecting pipe 8, the solar rays applied on the vacuum tube 6 are condensed efficiently and solar heat is absorbed by the heat collecting pipe 8 having the selective absorbing film 9 with only a small amount of heat radiation, so as to exchange heat with the heat medium 1. Thus, since the heat collcting surface area of the heat collecting pipe 8 is reduced, the loss of heat radiation from the pipe 8 is reduced and it is possible to enable the solar heat collector to keep a high heat collecting efficiency even at the time of high temperature heat collection.