To eject sheets after forming images without waiting restoration of a sheet processor even when the sheet processor does not operate.

An image forming system 1 selects both face conveying passages 174 with a switching member 175 when a sheet detection sensor S201 detects an abnormal state of the sheet processor 2. Thereafter, the maximum stored number of the sheets stored in a circulation guide passage 177 is counted with a sheet feed counter to stop a sheet feed part 146. Furthermore, the final sheet of the maximum stored number passes a switching member 195, and then a preliminary ejection passage 190 is selected with the switching member. Thereby, even when the sheet processor does not operate, the sheets after forming the images are ejected out of the system without waiting restoration of the sheet processor.