Image forming system including at least one image forming apparatus for forming images on sheets on the basis of image data. At least one temporary containing apparatus is disposed downstream of the image forming apparatus for temporarily containing therein the sheets on which the images have been formed. A separating and conveying apparatus separates and conveys the sheets contained in the temporary containing apparatus one by one. A sheet post-processing apparatus conveys the sheets conveyed by the separating and conveying apparatus and the sheets on which the images have been formed by the image forming apparatus and which bypass the temporary containing apparatus in an arbitrary order, in order to effect a set post-process on the conveyed sheets.