An image forming apparatus is provided with: an obtainer which obtains first information indicating a new toner cartridge having just been loaded thereon or a toner cartridge to be replaced with a new one and second information indicating the current condition under which a fusing process is performed for image forming; a determiner which determines the right type of a replacement toner cartridge to be loaded in place of the toner cartridge causing the first information obtained by the obtainer, based on the second information also obtained by the obtainer; an output portion which outputs an instruction to deliver a replacement toner cartridge of the type determined by the determiner; a detector which detects a new toner cartridge having just been loaded thereon; and a fusing processor which performs a fusing process under the optimal condition based on the amount of the toner supplied from the detector's detected new toner cartridge which is a replacement toner cartridge delivered according to the delivery instruction outputted by the output portion.