1. A radiation imaging system for dividing a total image capture field into N integer number of small image capture fields, and producing a single continuous radiographic image from N number of division radiographic images obtained by division exposures of said small image capture fields, said radiation imaging system comprising: a radiation source for emitting radiation to each of said small image capture fields; a radiation image detecting device having a detection panel having an imaging surface having an arrangement of a plurality of pixels, said detection panel detecting said radiation that has passed through a body part of said small image capture field to produce said division radiographic image; a plurality of dose detection sensors substantially uniformly distributed in said imaging surface, each for measuring a radiation dose; a memory for storing an irradiation area map that defines as an irradiation area an area for measuring said radiation dose in accordance with said body part to be imaged; a dose detection sensor selector for selecting one or more of said dose detection sensors belonging to said irradiation area based on said irradiation area map; and an automatic exposure controller for automatically controlling a radiation exposure in each of said division exposures, said automatic exposure controller stopping emission of said radiation from said radiation source in accordance with a measurement value obtained from a detection signal of said dose detection sensor selected by said dose detection sensor selector.