To provide a pipe cutter that can easily cut pipes of various diameters via smooth and appropriate drive control on its cutting tools relative to the pipes.

A support member 24 with an internal gear 24a is disposed at the tip end of an outer pipe 21 of a main spindle 2, a sun gear 23a is arranged at the tip end of an inner pipe 23 of the main spindle 2, and a plurality of planet gears 25 are placed in mesh with the sun and internal gears 23a and 24a. The shafts of the planet gears 25 fixedly carry a plurality of arm members 27, on which a plurality of cutting tools 28 are supported. Driving or rotating the outer and inner pipes 21 and 23 in the same direction with a rotational difference caused in between, relative to a pipe supported against rotation causes each planet gear 25 to rotate and at the same time revolve about the sun gear 23a, with the result that each arm member 27 is swung and each cutting tool 28 is moved radially as it is revolved to cut the pipe.