PURPOSE: To facilitate the assembly of a solar heat collector, to protect both ends of each of heat collecting elements and to secure the watertightness of every connecting part of the solar heat collector by using pipe casings made of a resin material having a high anticorrosive property.

CONSTITUTION: A pipe casings 19 are produced in such a manner that an integrally molded resin product 26 comprising a couple of box-shaped sections 24 held in communication with each other through a tubular section 25 is cut through the tubular section 25. In this case, the tubular section 25 is so cut that a plurality of heat collecting element fitting holes 28 communication with one another through pipe insert ports 27 are formed in each of the cut surfaces of the tubular section 25 and the inner spaces within the product 26 are made to communicate with each other so as to make the molding of the resin material such as a blow molding process performed without any hindrance. As the resin material for producing the molded product 26, polyethylene resin mixed with carbon black powder is desirable in view of its weatherproof and heat resistant properties and its strength.