To cut evenly the outer surface of a resin pipe even though it is a winding pipe wound in a coil form after the formation, or the like, by moving a cutter guide body along the inner surface of the resin pipe, and moving a cutter integrally with the cutter guide by maintaining a set interval to the cutter guide body.

A cutter guide body 1 is slid and moved in the peripheral direction along the inner surface of a resin pipe P1. Following that, a feed roller 15 at the outer side of the resin pipe P1 and a cutting tool 17 are moved in the peripheral direction along the inner surface of the resin pipe P1, the feed roller 5 pressure-contacted to the outer surface of the resin pipe P1 is rotated through a projection line, the cutter guide body 1 is being inserted to the inner side of the resin pipe P1, and the roller 15 and the cutting tool 17 are also to be inserted to the outer side of the resin pipe P1, together with the cutter guide body 1.