An image forming system includes a post-processing unit capable of performing a post-processing on the sheet on which the toner image is formed. The image forming system is capable of executing a transfer cleaning operation to move toner from a transfer member to an image bearer by electrostatic force caused by cleaning bias applied by a bias applying unit in a state where the image bearer and the transfer member are rotated, to clean the transfer member, as an inter-sheet operation performed when at least one of inter-sheet areas that exist on the image bearer during a successive image forming period. The image forming system is capable of executing a rotation stop operation to stop rotation of the image bearer and the transfer member, as the inter-sheet operation when the post-processing is performed, in addition to the transfer cleaning operation, before or after the transfer cleaning operation is executed.