To provide a paper post-processing device and a document processor reducing motor malfunction caused by the adhesion of brush abrasion powder without having influence on productivity and conveying quality.

The paper post-processing device and the document processor includes: a means of communications communicating with an image forming device; one or more post-processing units passing the paper ejected from the image forming device when receiving an instruction for shifting to a predetermined paper passing mode from the image forming device by the means of communications, and with a driving source of a DC brush motor for performing various kinds of post-processing based on the passing paper mode with respect to the paper; a post-processing control means performing the operation control of the post-processing unit in the paper passing mode; a driving execution propriety determination means determining whether or not a fixed time drive driving the DC brush motor for only predetermined drive time irrespective of the operation control during the operation control of the post-processing unit in the paper passing mode can be executed; and a motor drive means executing the fixed time drive when it is determined that the fixed time drive can be executed.