Post-processing apparatus and image forming apparatus

The invention provides a post-processing apparatus and an image forming apparatus. The post-processing device is characterized by being provided with: a means for performing post-processing; and a guide member that guides the unit to a position at which the unit performs post-processing, the first guide part extends along the width direction of the medium; the second guide part is arranged at the end part of the first guide part, is inclined relative to the width direction of the medium and guides the unit to a corner of the medium; a third guide portion disposed at an end portion of the first guide portion and extending branched from the second guide portion; and a fourth guide portion connecting the second guide portion and the third guide portion. And a branching member that is disposed at a portion where the second guide portion and the third guide portion branch, guides the unit from the first guide portion toward the second guide portion, and guides the unit from the third guide portion toward the first