An image forming system includes a first sheet stacking device including a rack, provided downstream of an image forming apparatus in a conveyance direction of a recording sheet and connected with the image forming apparatus, for stacking the recording sheet delivered from the image forming apparatus; a second sheet stacking device, which is provided downstream of the first sheet stacking device and connected with the first sheet stacking device; and a controller for controlling the image forming apparatus and the first and second sheet stacking devices. At least one of the first and second sheet stacking devices has a job stop button for stopping a printing job, and when the job stop button is turned on while the printing job execution is in progress, the controller controls the sheet stacking device to stop a stack of a recording sheet to the rack.