To appropriately center an X-ray beam in a target for forming a radiographic image.

A field definer is set at a position between an X-ray source and an X-ray detector where a target is to be set. The field definer comprises a pair of stoppers between which the target can be located. The stoppers can be relocated in the mutually horizontal directions adjacent to the target. A sensor communicating with the stoppers produces signals determined based on the distance between the stoppers. A control device, utilizing the signals, makes the X-ray source irradiate an X-ray beam to a requested region in the field between the stoppers. For example, the X-ray source is collimated so that the X-ray beam is irradiated only to the target between the stoppers, the target being set between the stoppers, which are adjusted to abut to the target.