An X-ray imaging device and method acquiring a long-length image that is connected. A configuration data of the signal intensity depending on the position along a moving direction of the long-length imaging is acquired by acquiring a model data prior to the long-length imaging, to obtain an approximate configuration A long-length imaging is conducted and a brightness difference takes place along the data line in overlapping pixel regions relative to two X-ray images adjacent each other. An offset correction value C in pixels in the region other than the pixel regions from the difference Δ of pixel values in such overlapping pixel regions, the slot width D and the overlapping width d. An offset correction is conducted based on such offset correction value, C and the X-ray images following the offset correction are connected to generate the long-length imaging to obtain a long-length image that is naturally connected.