A radiation imaging apparatus comprises: a detector that includes a detection unit in which pixels having a conversion element that converts radiation to an electric charge are arranged in a matrix shape, a drive circuit that drives the detection unit, and a read circuit that outputs an electric signal corresponding to the electric charge as image data; a radiation detection unit that detects a radiation irradiation state at a plurality of positions in the detection unit; and a control unit that controls operations of the drive circuit and the read circuit in accordance with a detection result obtained by the radiation detection unit, wherein the radiation detection unit detects a radiation irradiation state at least at a center region and a peripheral region in the detection unit, and a detection capability at the center region is set to a higher capability than a detection capability at the peripheral region.