To prevent falling and the loss, while reducing labor and time for cutting a pipe to be cut having a recess-projection in the longitudinal direction.

This cutting tool 7 cuts the pipe to be cut 2 having the recess-projection in the longitudinal direction by a cutting blade 4 such as a saw blade 3; and forms a gate-shaped tool body 8 engaging with recess-projection parts 5 and 6 of the cutting object pipe 2 and straddling the pipe to be cut 2. This tool body 8 forms a cutting blade guide hole 15 for vertically cutting the pipe to be cut 2 while holding and reciprocatably guiding by inserting the cutting blade 4.