A sheet processing system includes a sheet processing device that includes a post-processing unit that performs a predetermined post-processing on a sheet member and a sheet supplying device that supplies the sheet member to the sheet processing device. The post-processing unit has two waiting positions including a first position that is a normal waiting position and a second position that is a position filling items to be used in the post-processing in the post-processing unit. When the post-processing unit moves from the second position to a post-processing position to perform the post-processing in response to a post-processing request, the sheet supplying device sets a supply time for supplying the sheet member to the sheet processing device longer than a time that is required for the sheet processing device to move from the first position to the post-processing position by a predetermined time.