Abstract: A pipe supporting mandrel for use in connection with a mandrel rod of a pipe bending machine includes a hose-like part of flexible material hermetically sealed at both ends thereof and being provided at one end with a connecting piece attachable to the mandrel rod. The mandrel rod and connecting piece having a throughgoing passage for admitting a pressure medium into the flexible hose-like part. Before the start of the bending process, the flexible hose-like part is inserted into the region of the pipe to be bent and after inflation by the pressure medium it firmly engages against the inner wall of the pipe. After completion of the bending the hose-like part is deflated and the entire mandrel is withdrawn from the pipe.