PROCESSING DEVICE, PROCESSING PROGRAM, PROCESSING METHOD, AND PROCESSING SYSTEM

To provide a processing device or the like that is suitable for processing an image obtained by photographing the inside of an oral cavity to be used for intraoral diagnosis. Provided is a processing device comprising: an input/output interface which is communicably connected to a camera for capturing an image, of a subject, at least including an oral cavity, and which is configured to receive an input of the image captured by the camera; a memory which is configured to store the image received by the input/output interface in addition to computer readable instructions; and a processor which is configured to, through execution of the computer readable instructions stored in the memory, specify a prescribed area in the subject included in the image on the basis of the image stored in the memory, and to process the image in such a manner as to render the specified prescribed area identifiable.