An image forming apparatus in an image forming system including: a first tray that feeds recording media; a second tray that feeds recording media; and a reading section, wherein the image forming apparatus includes: a controller; and an image forming section that forms images on the recording media fed from the first tray and second tray. The reading section is configured to read the images formed on the recording media fed from the first tray and second tray. The controller, while performing a print job on the recording media fed from the first tray: prints, using the image forming section, a front-to-back registration adjustment chart on a recording medium fed from the second tray; reads the printed front-to-back registration adjustment chart using the reading section; and performs a front-to-back registration adjustment for the second tray based on the read front-to-back registration adjustment chart.

An image reading device reads an image on a sheet conveyed along a conveyance path. The image reding device includes a reading sensor, a lifting device, and a conveyance guide. The reading sensor optically reads the image. The lifting device lifts and lowers the reading sensor to a reading height which is close to the conveyance path and at which the image can be read and a non-reading height which is separated from the conveyance path more upwardly than the reading height. The conveyance guide is disposed above the conveyance path and guides the sheet to an image reading position by the reading sensor. The conveyance guide is pushed down by the reading sensor lowered to the reading height, and is displaced from a retracted posture separated upward from the conveyance path with a predetermined interval to a guiding posture closer to the conveyance path than the retracted posture.