A radiation imaging apparatus is provided. The apparatus comprises a scintillator configured to convert radiation into light, a sensor panel in which a plurality of pixels each comprising a light detector configured to detect the light is arranged, and a processing unit. The processing unit comprises a conversion unit configured to output a detection signal in accordance with a signal generated in the light detector by the incident light and radiation that has transmitted through the scintillator without being converted into light, and a reset control unit configured to determine that the light detector detects the transmitted radiation based on a magnitude of the detection signal and reset the conversion unit if the light detector is determined to detect the transmitted radiation.
