PURPOSE: To permit the speedy assembly and surface fitting of the pipes having different pipe diameter by using a jig by an operator by installing a pipe pressing bolt which presses and fixes the periphery of a pipe for fitting the edge part with the pipe edge of the other pipe press-fixed between a pipe receiving member and a pipe pushing member and performs surface joining.

CONSTITUTION: When pipes A and B are assembled, the part in the vicinity of the pipe edge of the pipes A is surrounded by a frame body 2, and the pipe A is nipped between a pipe pushing member 11 and the pipe receiving members 7 and 8 by operating a handle 10 and fixed. Then, the pipe a and the assembled pipe B are placed onto the pipe receiving members 7 and 8, and the pipe edge surfaces are fitted, and the interval between the both pipes is set to a prescribed route interval, and then, a lever rod 12 is allowed to get over the joint parts of the both pipes A and B by inserting the lever rod 12 into the pipe pressing member 11, and the pipe pushing bolts 13 and 14 are screwed onto the both edges of the lever rod 12, and the peripheral surfaces of the pipes A and B are pushed by the top edge. Then, the pipes A and B are firmly fixed, and the pipe pushing bolts 13, 14, 15, and 16 are properly, screwed, and surface fitting is performed by minutely changing the position of the pipe B. Then, the posterior tentative fitting welding is performed.