PURPOSE: To minimize temperature gradient occurring during sawing in the whole saw blade including cutting edges for the purpose of preventing the generation of the strain in the whole circular saw blade by heating non-heat generating part during sawing excluding cutting edge of the circular saw blade.

CONSTITUTION: At proper positions of a circular saw blade 1 are thermosensors 5W9 attached, and in addition, a superheater equipment is attached at a portion of saw other than cutting edges 3 holding the circular saw 1 on both sides. When sawing a workmaterial the cutting edges 3 are heated by frictional heat caused by the friction with workmaterial causing temperature gradient from other portion. The strain in the whole saw blade can be minimized by detecting the temperature gradient by the sensors and giving a required quantity of heat to low temperature portions through the superheater equipment.