To accelerate correction processing and reduce memory capacity in an apparatus of reading radiation image information which obtains one pixel of a final image by adding and correction processing of output from a plurality of photoelectric conversion elements adjacent to a line sensor in the longitudinal direction of the line sensor.

Data S' of an intermediate image is obtained by adding three by three of outputs Q from each photoelectric conversion element 21 of the line sensor 20 with an adding means 31, and data S of the final image is obtained by correction processing to data S' of the intermediate image having a small amount of data with a correcting means 32.