A radiation imaging apparatus includes an imaging area including a plurality of conversion elements configured to convert a radiation into an electrical signal, a detection element provided in the imaging area and configured to detect the radiation, a reading unit configured to read signals of the conversion elements and the detection element, and a control unit configured to execute radiation exposure amount control in capturing a radiation image by a control method selected from a first control method and a second control method based on an imaging condition in capturing the radiation image, the first control method controlling an exposure amount based on the reading result of the detection element read by the reading unit during radiation irradiation, the second control method controlling the exposure amount based on a pixel value of the radiation image, the radiation image being based on the signals of the plurality of conversion elements.
