A radiation imaging apparatus having high frame rate and picture quality by offset correction has: a sensor array having matrix-shaped pixels each including a converting element and a TFT; a driver for supplying signals to control terminals of the TFTs row by row; a reader for holding a signal in a first or second sampling/holding (S/H) circuit and outputting an image signal; and a controller for controlling the driver and reader. Until the image signal is output after irradiation of the apparatus with pulsating radiation, the TFT of a pixel is driven so as to output a first signal, the TFT of the pixel to which the first signal has been output is driven so as to output a second electric signal, and the reader outputs the image signal of the signal showing a difference between the first and second signals held in the first and second S/H circuits.