To arrange a large number of small caliber pipes densely by inserting metal short pipes in the pipe ends of the small caliber pipes comprising a thermoplastic resin, fusing a thermoplastic resin plate to the pipe ends of the small caliber pipes, and removing the resin in the inserted short pipes and the short pipes.

A metal short pipe 2 is inserted in the pipe end of each of resin pipes 1, a Teflon sheet 3 is placed on a hot plate 4 as a release sheet, and a resin plate 5 having the same quality as the resin pipes is placed thereon to be heated and softened. When the resin pipes 1 is slowly pressed on the resin plate 5 by light force, the metal short pipes are held in the softened resin plate 5 so as to punch the resin plate 5 to reach the Teflon sheet while the resin pipes 1 come into contact with the resin plate. When the resin pipes are further pressed to the resin plate after the elapse of several min, they stop at the non-softened area of the resin plate and the previously softened parts thereof are perfectly fused to the resin plate. After cooling, the Teflon sheet is easily peeled and the leading end of a fine rod having the same quality as the resin plate is heated and brought into contact with the softened resin parts. The fused resin is pulled out and removed.