An image forming apparatus may include a first tray configured to accommodate one or more recording sheets to be supplied to an image forming unit, a body frame configured to position an upper part of the first tray, and an expansion members disposed under the body frame to position a lower part of the first tray. The expansion member may include a transmission mechanism configured to be engagable with a body-side gear provided in the body frame. The transmission mechanism may be configured to transmit a drive force, which is transmitted from a drive source provided in the body frame via the body-side gear, to an add-on mechanism, when the transmission mechanism is engaged with the body-side gear.