1. A printer, comprising: an image memory in which different kinds of image data can be stored, the image data corresponding to different patients and being stored with reference to the order in which the image data are stored in the image memory; a printing unit that prints images based on the image data stored in the image memory; a controller that manages the image data stored in the image memory and controls the printing unit; and a determination configuration that determines that a patient is different from another patient by detecting a period of signal information in the image data, wherein, when the determination configuration determines that a kind of the image data presented for storage in the image memory is different than that of a last stored image data, the controller causes the printing unit to print all images for the last stored image data and all precedingly stored image data of a same kind as the last stored image data so as to prevent captured images of a plurality of the patients to be printed on one recording sheet, and when the determination configuration determines that the kind of the image data presented for storage in the image memory is not different than that of the last stored image data, the controller causes the image data presented for storage to be stored in the image memory.