To provide a pipe cutting device which can cope with pipes having different diameters with one pipe cutting machine, in which the pipe cutting device can be easily mounted to a pipe to be cut and also can be easily operated, which has no looseness during cutting, and in which durability of a disc cutter is excellent.

The pipe to be cut is cut by the disc cutter after mounting a motor, which transmits power for rotating the disc cutter by a shaft, to a holding plate and moving the holding plate, which is laid on the pipe to be cut, and the shaft in parallel to a pipe axial core in the cutting face by a radial positioning device in the pipe cutting device. The radial positioning device is formed of at least a positioning plate and a cam mounted to the positioning plate in the pipe cutting device. The pipe can be cut from inside by supporting the shaft and the disc cutter to a pipe inner diameter while moving them in parallel by changing the angle of the cam to the positioning plate.