A radiation imaging apparatus connected to a radiation generation apparatus which generates radiation and a sensor which accumulates a charge corresponding to an irradiating dose on a detection surface acquires a radiation image by driving the sensor upon generation of radiation by the radiation generation apparatus and acquires a dark image by driving the sensor without generation of radiation by the radiation generation apparatus. The radiation imaging apparatus adjusts a driving timing of the sensor so as to set a time difference between two starts of reading charge from the sensor to acquire the radiation image and reading charge from the sensor to obtain the dark image to an integer multiple of a predetermined time.