A radiation image photographing apparatus capable of easily obtaining a high quality long length image representing the entirety of a subject by combining a plurality of images, without a noticeable step density difference at a joint, obtained by serially radiographing a plurality of adjacent areas of the subject using the same radiation source and the same radiation image detector, in which a photographing condition for performing each radiographing is obtained by a photographing condition obtaining unit, a photographable width in a long length direction in each radiographing is obtained by a photographable range obtaining unit from the photographing condition, and the plurality of areas of the subject is allocated by an allocation unit such that a photographing width in the long length direction in each radiographing does not exceed the photographable width.
