An image forming apparatus comprises an image former that prints target data on a sheet, a first judger that judges a supply unit that is replaceably loaded thereon and has a memory storing identification information uniquely given to the supply unit and information about a plurality of vendors providing the supply unit, is whether or not a reproduced product, an accessor that accesses a server owned by a vendor supplying the supply unit according to the information about the vendors providing the supply unit, which is stored in the memory of the supply unit, if the first judger judges that the supply unit is a reproduced product, a second judger that judges whether or not the identification information stored in the memory of the supply unit is registered in the server owned by the vendor supplying the supply unit, which is accessed by the accessor. Print operations performed by the image former are limited if the second judger judges that the identification information is not registered in the server, meanwhile, print operations performed by the image former are permitted if the second judger judges that the identification information is registered in the server.