1. A radiation image processing apparatus that performs image processing on a radiation image captured by applying radiation to a subject based on scattered radiation generated by the subject, the apparatus comprising: an area setting unit that, in performing the image processing on a processing target area of the image processing in the radiation image, adds another area different from the processing target area in the radiation image to the processing target area; and an image processing unit that performs the image processing on the processing target area using the another area and the processing target area.