A radiation imaging apparatus includes a pixel portion in which a plurality of pixels, each pixel including a conversion element configured to convert radiation into charge, are arranged in a matrix, a driving circuit configured to drive a plurality of driving lines and a processing unit configured to process a signal from the pixel portion. The driving circuit performs a reset operation in which the conversion elements of the plurality of pixels are repetitively reset. The pixel portion includes rows in which the pixels have been divided into a plurality of groups. The conversion elements of the plurality of groups are reset at different timings in the reset operation, and the processing unit corrects, by using a signal of a pixel of another group, a signal of a pixel of a group with data deficiency caused by the reset operation.