PURPOSE: To obtain a pipe body for heat insulation which has sealed annular space between an internal and an external circumferential wall by welding both end surfaces of the pipe in abutting relation while bending both ends outward to inward.

CONSTITUTION: Dies 12 are brought into contact with both ends 11a of one metallic pipe 11. The dies 12 are pressed as shown by arrows to make both ends 11a of the metallic pipe 11 abut to each other while turning both ends 11a of the metallic pipe 11 inside out. In another way, both ends 11a while bent inward abut to each other. The space 11d formed between the internal circumferential wall 11b and external circumferential wall 11c is evacuated and the abutting parts of both ends 11a are welded to form a pipe body 21 having the sealed annular space. A necessary number of the pipe bodies 21 are fitted lengthwise around a supply pipe for high or low temperature fluid to perform heat insulation, etc., of the supply pipe.