1. A radiation image processing apparatus comprising a processor implementing functions of: a storage unit configured to store a plurality of pieces of part information, each including an imaging part indicating a part of an object to be imaged and an extraction size of an extraction area on a radiation image; a recognizing unit configured to recognize a region of interest from a radiation image based on the imaging part included in designated part information among the plurality of pieces of part information; and an arrangement unit configured to arrange the extraction area with a predetermined extraction size in association with the designated part information on the radiation image in accordance with the region of interest recognized by said recognizing unit.