PURPOSE: To make the chamfered surface of plastic pipe-end into smooth low friction-surface by a method in which the end of a heated plastic pipe is covered with the outer mold whose inner diameter is equal to the outer diameter of the pipe-end, and then the diameter-expanding part of a diameter-expanding inner mold is inserted into said pipe-end, and the diameter of the inner mold is expanded.

CONSTITUTION: The end P of the plastic pipe softened under heating is covered with the molding part 31 of an outer mold 3 and the intermediate part of the chamber-molding face 30 of the inner end of said molding part 31 is positioned at the end (e) of the pipe. The outer peripheral side of the pipe-end (e) is pushed by the chamber-molding face 30, and the inner peripheral side of the pipe-end (e) deforms inside more than the inner diameter of the pipe-end. Next when the segment 190 of a diameter-expanding inner mold 4 is inserted into the end-part P of the pipe, and the pipe is expanded, the part which deforms inside more than the inner diameter of the plastic pipe-end P at the pipe-end (e) may be compressed. The tapered surface may be molded at the peripheral side of the pipe-end (e) by the chamber- molding face 30 of the outer mold 3. Then the segment 190 has the chamber-molding face 30 between he small diameter part 192 and the large diameter part 193, and the outer diameter of the large diameter part 193 becomes equal to the outer diameter of the pipe-end, and the outer diameter of the small diameter-part 192 becomes equal to the inner diameter of the pipe-end at maximum diameter-expansion.