To linearly cut an FEP pipe by providing a guide for fixing the FEP pipe, perform safety cutting operation without exposing a rotary blade of a cutting instrument, and further complete the operation in a short period of time.

A tool for longitudinally cutting the FEP pipe comprises the cutting instrument 3 including the rotary blade 2 for linearly cutting a pipe wall of the FEP pipe t in its longitudinal direction, a substantially cylindrical FEP pipe guide 4 having an inner diameter longer than an outer diameter of the FEP pipe t and an aperture 10 for bringing the rotary blade 2 of the cutting instrument 3 into contact with the FEP pipe t to support the FEP pipe t inserted therein, and a cutting instrument fixing part 5 for fixing the cutting instrument 3 to the aperture 10 of the guide 4. The tool can expand the FEP pipe t into a substantially planar form.