Post-processing apparatus for image forming apparatus

One embodiment of the present disclosure provides a post-processing apparatus for an image forming apparatus which arranges paper ejected from an ejection part of an image forming apparatus on a fence for post-processing. The post-processing apparatus includes a paddle guide which includes a paddle arm to which a paddle wing is coupled and a pusher positioned adjacent to the ejection part and stands by at a home position until the paper is ejected, a driving part which vertically moves the paddle guide, rotates when the paper is ejected from the ejection part to move the paddle guide downward so that the pusher presses the paper downward and drops the paper on a stacking base, and a paddle wing which vertically moves according to a vertical movement of the paddle guide, moves downward according to a downward movement of the paddle guide, arranges the paper dropped on the stacking base toward the fence positioned adjacent to the stacking base, and then, moves upward with an upward movement of the paddle guide according to operation of the driving part, wherein vertical movements of the pusher and the paddle wing are performed by a vertical movement of the paddle guide performed due to single unit periodic operation of the driving part.