PURPOSE: To easily perform centering work or tension adjusting work at the time of the attachment of an inner peripheral edge rotating cutting blade to a holding device within a short time even by an unskilled person.

CONSTITUTION: A holding device 20 is rotated around an axis O by a rotary motor 23 and the angle of rotation of the holding device 20 is detected by a rotary encoder 42 and the inner peripheral edge of an inner peripheral edge rotating cutting blade 10 is optically detected in a non contact state by a fixed end edge detection means 44 and the position of the inner peripheral edge of the cutting blade 10 to the rotary axis is displayed on a display device 58 in the relation with the angle of rotation.