PURPOSE: To eliminate the need for end surface processing after cutting by providing a heat-conductive blade for cutting, a heat generation body which heats the blade, a temperature detector which detects the temperature of the blade, and a controller which controls the heat generation body according to temperature information obtained by the temperature detector.

CONSTITUTION: The blade 2 is heated by a thermomodule 3, the temperature of the blade edge is detected by a thermocouple 4, and the obtained temperature information is fed back to the thermomodule 5, which is so controlled that the temperature of the blade edge is specific temperature. Further, the thermomodule 3 is arranged as near the blade edge as possible, a heat radiation plate is provided on the opposite surface from the surface contacting the blade 2, and parts except the blade edge and heat radiation plate are covered with a heat insulator. When a plastic optical fiber 6 is cut, the temperature of the blade 2 is controlled, so proper heat is given to plastic when the blade edge cuts the optical fiber 6 to reduce its viscosity, so that the blade edge carries on cutting the fiber smoothly. Consequently, an end surface which has uniformity to a certain extent is obtained only by the cutting th troublesome end surface processing after the cutting is not necessary.