To quickly and accurately cut pipes with a cutting blade having a small blade pitch by cutting a pipe while rocking the rotating cutting blade, and revolving the rotating cutting blade in the circumferential direction of the pipe.

In the case of cutting a pipe 11, a rotating motor 20 is firstly operated so that a cutting blade 54 is rotated at the predetermined velocity. Continuously, a cylinder rod 60 is moved backward by a turning cylinder 58 so that the rotating cutting blade 54 bites the pipe 11. At the time of making the rotating cutting blade 54 bite the pipe 11 for cutting, a rotor 32 is normally and reversely rotated so that the cutting blade 54 bites the pipe 11 while rocking. With this structure, a blade of the cutting blade 54 arranged in the circumferential edge can be moved in the core direction of the pipe 11 while maintaining the condition that the cutting blade 54 is always tightly fitted to a circular part of the pipe 11. In the case of cutting the pipes 11 having the same diameter, the cutting blade having a small blade pitch can be used.