PURPOSE: To easily bend a metallic pipe without damaging a covering layer, by inserting a bender body into a metallic pipe body, and giving a bending moment from the inside surface of the pipe by use of plural pressing dies fitted to the bender.

CONSTITUTION: A pipe bender is inserted into the inside of a metallic pipe 1 having a covering layer 20. On one side part of this bender body 2, pressing dies 3, 4 are placed, and on the other side, a pressing die 5 is placed. When a pressurized liquid is led into cylinders 7, 8 from a pressurized liquid hose 18, pistons 10, 11 are pressed and moved, also the pressing dies 3, 4 move against a return spring 14, contact with the inside surface of the metallic pipe 1, and by its reaction force, the pressing die 5 of the other side also contacts with the inside surface of the metallic pipe 1. When liquid pressure is further provided, force α by the pressing die 3, force β by the pressing die 4 and force γ by the pressing die 5 are provided to the inside surface of the metallic pipe 1, and the bender body 2 receives reaction force of said force α, β and γ. When liquid pressure is further provided to the pistons 10, 11, bend-working is performed to the metallic pipe 1 having the covering layer 20.