An image forming device is disclosed that is able to prevent halt of operations due to full memory occupation, and prevent the full occupation of the memory. The image forming device includes a reading unit; an image data storage unit; a vacancy waiting unit that, when allocating a storage area for storing image data in the image data storage unit, waits until the storage size of a vacancy in the image data storage unit becomes greater than a predetermined value when allocation of the storage area fails; a failure processing unit that, when allocating the storage area for storing the image data in the image data storage unit, performs failure processing when allocation of the storage area fails; and a control unit that controls one of the vacancy waiting unit and the failure processing unit according to image forming conditions in the image forming device.