Disclosed are treatment information display device and method for displaying treatment history on an image of teeth in an accumulated manner. The treatment information display method enables a user to recognize at once a past treatment history, a current treatment status, and a future treatment plan by displaying, on the image of teeth, treatment information for the past, present, and future. In addition, the treatment information display method can provide the user with pieces of treatment information displayed on different images of teeth, by displaying, in an accumulated manner, the pieces of treatment information displayed on a plurality of teeth images.