The purpose of the present invention is to provide a sheet post-processing apparatus which facilitates eliminating of a jammed sheet occurring in the path when sheets discharged from an image forming apparatus are stored as being sorted into two directions. The present invention comprises a sheet post-processing apparatus including a first conveying path through which a sheet introduced from a first introducing port is conveyed, a second conveying path through which a sheet introduced from a second introducing port is conveyed, and a stack portion which stacks sheets conveyed through the second conveying path and which is configured to have at least a part of the stack portion be swingable about an axis intersecting with a sheet conveyance direction of a sheet conveyed to the second conveying path between a stack position where sheets are stacked and an open position where the first introducing port of the first conveying path is opened.