Abstract: Apparatus including two types of cutting means or roller cutters and shears for cutting a channel box for a fuel assembly for a nuclear reactor and method therefor. The roller cutters and shears are located in the lower portion of a casing having inserted thereinto the channel box from which the fuel assembly has been removed, with the shears being located beneath the roller cutters. The roller cutters continuously cut the channel box axially thereof, while the shears shear the axially-split portions of the channel box in a direction intersecting the center axis of the channel box. Means for outwardly expanding the axially-split portions of the channel box is provided between the roller cutters and the shears. Means for downwardly moving the channel box in the casing is inserted in the casing. Means for drawing off coolant from the casing to clean the latter is connected to the upper portion of the casing.