PURPOSE: To make it easy to connect a connecting pipe of a heat collector element and a transparent pipe, by sandblasting a sealing metal fitment so as to roughen the surface thereof, forming an oxidized film thereon, welding glass thereonto, and removing the oxidized film by sandblasting.

CONSTITUTION: A molded body of a glass sealing alloy such as Kovar, 426 alloy or the like is formed to have an upright edge section 1 and an opening 2 in the central section by using a press. Then by blasting sand mainly consisting of alumina, the surfaces of the outer and inner sides of the upright edge section 1 are roughened as shown at 3. All the surfaces of the body are formed with a oxidized film 4 by wet oxidizing treatment. The sealing metal fitment that has an oxidized film formed after sandblasting exhibits improved wetability when glass is welded thereto, and the sealing can be carried out favorably without generating bubbles. Then a glass layer 5 is formed for covering the tip of the upright section 1. Then the oxidized films on the outer and inner surfaces of the opening 2 are removed by sandblasting.