A sheet treating apparatus for treating a sheet having an image formed thereon is provided, which includes a pair of transport rollers for transporting the sheet upward, a sheet post-treating portion having an intermediate treatment tray, provided to execute post-treatment such as sheet stitching or punching while holding the sheet in a substantially vertical state, and a sheet delivery portion arranged above the sheet post-treating portion. Also, an image forming apparatus is provided, which includes an image reading portion for reading an image, an image forming portion arranged below the image reading portion to form an image on a sheet, a delivery space portion provided in an apparatus housing between the image reading portion and the image forming portion to deliver the sheet, sheet treating portion for treating the sheet while holding it in a substantially vertical state, and an in-body transportation path for transporting the sheet treated by the sheet treating means to the delivery space portion.