PURPOSE: To provide the inexpensive method capable of smoothly bending a pipe and protecting the bent part light in weight without flattening or crushing the pipe by forming an insertion part to which plural flexible bar-like materials are inserted in a bundle.

CONSTITUTION: When a pipe 3 is bent while a spacer for bending the pipe is inserted into the pipe 3 such as a copper pipe as it is, it can be bent easily into a shape such as a desired vent or elbow. Since an individual bundled bar- like material 11 works separately in accordance with the bent shape of the pipe 3, the resistance caused by inserting the spacer for bending the pipe can be reduced. On the other hand, since the insertion part 1 having a diameter nearly the same as the inside diameter of the pipe made by bundling the bar-like materials 11 is inserted into the pipe, crushing of the pipe diameter is prevented surely from the inner part. Since the spacer for bending the pipe is made of synthetic resin, etc., and light in weight and excellent in workability in construction, it can be left inserted into the pipe 3 as it is under construction and the insertion part 1 serves as a protector.