PURPOSE: To form optional medium paths for regulating temperature excellent in airtightness and watertightness by forming grooves for forming the temperature regulating medium paths to one side or the facing surfaces of both sides of members to be combined mutually and then, sealing the facing surfaces of both sides to spread and join the surfaces.

CONSTITUTION: After the annular grooves 5 for the temperature regulating medium paths with a prescribed cross-sectional shape are formed by machining work, etc., the facing surfaces 3 and 4 of the members 1 and 2 are allowed to abut on each other. Next, after peripheral parts 6 are both sealed and tacked by electron beams, the brazing, etc., in a vacuum chamber, the facing surfaces are spread and joined by a HIP device. In this way, the temperature regulating medium paths excellent in the watertightness and the airtightness can be formed.