A radiation imaging apparatus is provided. Each pixel includes a signal generation unit configured to generate a pixel signal, a reset unit configured to cause the signal generation unit to generate an offset signal by resetting the signal generation unit to a state before the accumulation of charges, and a holding unit. The apparatus comprises a control unit configured to control each pixel to generate the pixel signal and the offset signal in every frame period and hold the pixel signal and the offset signal in the holding unit; and a readout unit configured to read out, from the holding unit, the offset signal generated in a frame period and the pixel signal generated in accordance with charges accumulated subsequently to the generation of the offset signal, and calculate a difference between the readout offset signal and pixel signal.