A printing apparatus includes: a holder in which a printing material cartridge set is mounted; and a mounting detection circuit for detecting mounted states of printing material cartridges in the holder. Each of the N printing material cartridges includes a storage device for storing information regarding a printing material which is contained, an electric device for mounting detection, a terminal for the storage device, and a terminal for the electric device. The electric devices of the N printing material cartridges are configured so that a detection voltage becomes equal to or greater than a threshold voltage set in advance when the N printing material cartridges are all mounted in the holder.