Pipe cutter

The utility model discloses a pipe cutting knife, which belongs to a manual cutting tool and solves the problems that the existing pipe cutting knife is difficult to reliably restrain a pipe when cutting the pipe with a smaller outline due to the fixed size of a pipe restraining groove, and the pipe moves and shakes in the cutting process to cause unevenness and deflection of a notch. According to the utility model, the plurality of moving parts which can extend to the pipe restraining groove and can retreat from the pipe restraining groove are arranged on the bearing body in the front-back direction, and the pipe restraining groove is shrunk when the moving parts extend to the pipe restraining groove, so that the pipe restraining groove is suitable for restraining pipes with smaller specifications; and when the moving piece retreats from the pipe restraining groove, the pipe restraining groove is expanded so that the pipe restraining groove can be suitable for restraining the pipe with the large specificatio