The first cutter that cuts, in the direction transverse to the unwinding direction, a continuous sheet of additional member unwound and drawn by a length in accordance with the thickness of the book block is arranged at the input port of the trimming station, the transport mechanism that transports the cut additional member from the first cutter out in the unwinding direction of the continuous sheet of additional member is arranged downstream of the first cutter, the second cutter that trims the cut additional member being transported on the transport path in the unwinding direction is arranged in the transport path of the transport mechanism, and the position of the blades of the second cutter may be adjusted in the direction transverse to the unwinding direction in accordance with the head-to-foot length of the book block.