An apparatus for trimming paper rolls or logs (2) including: a section for the entry of the logs (2) to be trimmed; a section for the exit of the trimmed logs (2′); a station with a cutting device (6) for trimming the logs (2); a device (3) for moving the logs (2, 2′) between the entry section, the cutting station and the exit section; a device (4), associated with the log-moving device (3), for retaining the logs when subjected to movement.