A built-in camera installed in an equipment for taking a photograph of a desired portion of an object to be photographed is positioned by (i) preparing a sensor which transmits a detection signal when it detects the object to be photographed, (ii) defining, when the detection signal varies by a predetermined value or greater, a certain portion of the object situated along the sensor axis as a particular portion of the object, (iii) determining in advance the desired portion of the object to be photographed relative to the particular portion of the object, (iv) fixing an optical axis of the built-in camera relative to the sensor axis in such a manner that the optical axis of the built-in camera is directed toward the desired portion of the object when the sensor axis is directed toward the particular portion of the object, (v) changing an orientation of the sensor axis toward the particular portion of the object, and (vi) causing the built-in camera to take a photograph of the object when the detection signal indicates that the sensor axis is directed toward the particular portion of the object.