A radiation imaging apparatus, comprising a sensor panel including a sensor array on which a plurality of sensors arranged in an array form and a scintillator layer provided on the sensor array, and a unit configured to perform signal processing based on a signal from the sensor array, wherein the sensor array includes a peripheral region and a central region located inside the peripheral region, the scintillator layer is disposed over the peripheral region and the central region so as to have uniform luminance efficiency with respect to the sensor array, and the unit performs the signal processing by using only signals from sensors disposed in the central region, of signals from the plurality of sensors, output from the sensor panel.