To effectively connect to a vacuum evacuation system and to facilitate welding sealing by pouring working fluid from a working fluid inlet provided in one surface of two metal plates to seal it.

A double-sided adhesive brazing sheet 6 is sandwiched between metal plates 2A and 2B made of two aluminum plates. The plate 2A is bulged at a central part in a tray state by pressing, and a pouring inlet 5 of working fluid 4 is passed from an upper surface to a lower surface at a flat surface of an end side protruding in a protruding state. The plate 2 is a flat plate having the same shape of its flat surface shape as the plate 2A. When the sheet 6 is heated while light pressure of the degree for not deviating the plates 2A, 2B sandwiching the sheet 6 is being applied, the three parties are integrally brazed at peripheral edges except the bulged part on the tray state at the center. Its heating temperature is generally at about 600°C according to a type of the sheet 6.