1. An X-ray photographing apparatus comprising: an X-ray generator configured to generate an X-ray; an X-ray detector configured to detect the X-ray that is transmitted through an object; and a panel that is provided between the X-ray generator and the X-ray detector and configured to contact the object, wherein a distance between a center axis of the X-ray generator and the X-ray detector is maintained to be uniform during a time period, and a radiation angle of the X-ray generated by the X-ray generator with respect to the object changes over the time period.