A controller determines a lower edge position of an imaging area of an image combined in long-length imaging through light illumination from a line marker. Thereby the controller performs control such that light from the line marker is switched off beyond an area, set in advance, capable of being imaged upon determination of the imaging area. Consequently, an operator just performs operation while looking at only light from the line marker upon determination of the imaging area, which achieves easy operation. As a result, operation upon determination of the imaging area can be facilitated.