Abstract: A dental X-ray irradiation indicating device which permits accurate indication of a location to be X-rayed and also permits photographing of an image substantially with the exact size. The device comprises a supporting member, an arm means extending from the supporting member, and an indicating member mounted on the arm means by way of a mounting member, whereby the indicating member is positioned in an opposing relationship to an intra-oral X-ray film package which is held in a predetermined angular position in an oral cavity of a patient. When an intra-oral X-ray photograph is to be taken, an X-ray is irradiated with reference to the indicating member of the device.