A pipe cutting device for a bookbinding machine comprises a pipe holder frame, a cutter carrier, a pipe cutting tool rack, a swinging plate and a hot riveting rack, wherein the pipe holder frame is connected with the cutter carrier; a sliding cavity is formed between the pipe holder frame and the cutter carrier; the pipe cutting tool rack is arranged in the sliding cavity in a sliding manner; a blade is arranged at the front end of the pipe cutting tool rack; the swinging plate is in movable connection with the hot riveting rack, the upper end of the swinging plate is connected with the pipe cutting tool rack, and the pipe cutting tool rack reciprocates in the sliding cavity along with the swinging plate; the swinging plate comprises a pipe cutting segment, a pipe baffling segment and a pipe falling segment which are sequentially arranged from the upper end to the other end, and a pushing device used for pushing the swinging plate to act is arranged on the hot riveting rack. The pipe cutting device has the advantages of high pipe cutting efficiency, good pipe cutting cooperativity and capability of finishing pipe baffling, falling and cutting actions.