If a control unit of a radiation image capturing apparatus acquires dark image data before photographing and at the same time detects initiation of irradiation of radiation based on image data read out by carrying out a readout process of the image data, the control unit applies off-voltage to all the scanning lines and shifts to an electric charge accumulation mode, and after the irradiation is over, sequentially applies on-voltage to each of the scanning lines, causes the scanning lines to carry out readout process of main image data from each of radiation detection elements, and subsequently acquires offset data in a condition where radiation is not irradiated to correct the main image data read out by the photographing or main image data read out by a photographing carried out after the former photographing based on offset lag part calculated from the offset data and the dark image data.
