A toner-conveying device includes a movable plate. The movable plate is movable between a holding position such as to couple a cap of a toner container to a nozzle when the toner container is supported by a container holder, and a retreating position such as not to hinder loading or unloading of the toner container in the container holder. The movable plate is placed in the holding position by a cam when the nozzle is coupled to the cap, and is released and moved to the retreating position while the toner container is being loaded or unloaded. In this structure, the cap can be properly positioned in the conveyor device while ensuring the rigidity of a bag of the container within a practically preferable range, without reducing the convenience for the operator.