To provide a bender for a pipe for forming an exhaust pipe, in which an exhaust gas can smoothly flow, while a pressure wave hardly reflects on the way.

A high-pressure pump 105 for pressurizing the water in a material pipe 31 is connected with a first plugging means 32 for plugging one end of the material pipe 31 under the pressure corresponding to the curvature radius of the part to be bent in the material pipe 31.