PURPOSE: To facilitate the maintenance and inspection of a rotary blade of a disk cutter for cutting waste culm supplied in fallen state into small pieces with a number of rotary blades attached to a pair of horizontal rotary shafts.

CONSTITUTION: A rotary shaft 2 in a pair of rotary shafts is supported by both side plates of a cutter case 5 and the other rotary shaft 3 is supported by right and left bearings 8, 8 attached to the rear plate 7 of the cutter case 5. The rear plate 7 is constructed to be rotatable backward around the lower axle 9 at least to a nearly horizontal position. When the rear plate 7 is rotated, the rotary shaft 3 and the rotary blades 4 supported by the bearings 8, 8 on the rear plate 7 are positioned above the rear plate 7 to completely expose the upper side and facilitate the maintenance and inspection of the blade.