To provide a bending tool for piping with which the flattening in the cross section of a pipe generated when piping by bending the pipe is prevented, and no trouble of the breakage of the pipe occurs.

This tool is a bending tool for piping for preventing the excessive bending and flattening of a flexible pipe by inserting it into the flexible bending piping when performing the bending piping of the piping material. The bending tool for piping has a bellow structure in which ribs having height 4, width 1 and tip width 3 are provided in the perpendicular direction to the axis direction at every constant interval 2 on the surface of a cylindrical body having a somewhat smaller diameter than the inside diameter of the pipe of a piping material which is ready to perform the bending piping. In this bending tool for piping, when expressing the stipulated bend radius of the piping material which is ready to perform the bending piping as R and the bend radius of the bending tool for piping as r, the ribs are designed so as to satisfy the each value 4, 1, 2 so that the r satisfies the relationship of R≥r (Each numerical value is mm).