1. A radiation imaging apparatus configured to capture radiographic images, the radiation imaging apparatus comprising: a radioactive ray generating unit configured to irradiate a subject with a plurality of radioactive rays generated at different radiation angles; a radioactive ray detection unit configured to capture a plurality of first radiographic images based on detection of the plurality of radioactive rays that have passed through the subject at the different irradiation angles; an area specification unit configured to specify an object area using the plurality of first radiographic images captured by the radioactive ray detection unit; and a determination unit configured to determine at least one radiation angles of the radioactive ray generating unit based on the object area specified by the area specification unit, wherein a second radiographic image is captured based on radioactive rays of the determined angle generated by the determination unit.