1. A radiographic image processing device comprising: an image acquisition section that acquires a subject image which is a radiographic image captured by an imaging system that includes a radiation source that irradiates a subject with radioactive rays, a shield that partially shields the radioactive rays emitted to the subject, and a radiation detector that detects the radioactive rays passed through the subject, the subject image being detected under a predetermined imaging condition by a shielded detection portion which is a portion of the radiation detector where the radioactive rays are shielded by the shield in an irradiation direction of the radioactive rays from the radiation source and a non-shielded detection portion which is a portion of the radiation detector excluding the shielded detection portion; an area information acquisition section that acquires area information which is information for specifying a non-shielded image area indicating a pixel value corresponding to each position in the non-shielded detection portion in the subject image and a shielded image area indicating a pixel value corresponding to each position in the shielded detection portion in the subject image; and a scattered ray suppression section that estimates, based on the imaging condition and the area information, spreading of scattered rays generated in a non-shielded subject portion which is a portion of the subject that transmits the radioactive rays in the irradiation direction of the radioactive rays from the radiation source in the subject image, estimates that scattered rays that spread to the non-shielded image area from a shielded subject portion which is a portion of the subject where the radioactive rays are shielded by the shield in the irradiation direction of the radioactive rays from the radiation source are not present, calculates a scattered ray component in each position in the non-shielded image area as the estimated scattered rays reach each position in the non-shielded image area, and suppresses the scattered ray component in each position in the non-shielded image area according to the calculated scattered ray component.