At least two first offset images having different accumulation times are acquired in a state in which radiation is not emitted. A pixel signal is read in an accumulation time shorter than that of a plurality of first offset images or using binning reading in a state in which the radiation is not emitted to acquire a second offset image. A reference image is acquired by reading the pixel signal using the same reading method as that used for the second offset image and in a state in which gates of the pixels are turned off. A difference between the two first offset images having different accumulation times is calculated to acquire a first dark current distribution image. A difference between the second offset image and the reference image is calculated to acquire a second dark current distribution image. It is determined whether or not reacquisition is needed on the basis of a correction error of a corrected image obtained by correcting the first dark current distribution image on the basis of the second dark current distribution image.