To perform a replacement work easily and rapidly by removing a cutter holder from the drive shaft of a motor while holding the holder and moving the cutter holder in a perpendicular direction to the axial direction of an extruder and further rotating the holder at right angles to remove the holding action and rotating the holder at right angles on a receiving table to fit the holder to the drive shaft of the motor from the downstream side of a cylinder.

A clamping member for the drive shaft 104 of a cutter holder 100 and the drive shaft 116 of a drive motor 114 is removed and a holding device 32 as a whole is moved perpendicularly to the drive shaft of an extruder to unload the holder 100 from a cutter box 110. Next, an arm 40 is rotated 90° perpendicularly to the shaft of the extruder using a rotation manipulating handle 38, and the holding device 32 is disposed on a receiving table with the assistance of a balancing machine with a cutter part set at the lower part and the arm 40 is rotated 90° perpendicularly to the shaft of the extruder using the handle 38 while a new holder 100 previously disposed is held. Thus the drive shaft 104 and the drive shaft 116 are connected to each other. Consequently, it is possible to save the burden of an operator and easily and rapidly replace even a large-size cutter holder 100.