High frequency offset component information is previously acquired from a solid-state radiation detector. Low frequency offset component information is acquired from the solid-state radiation detector before an operation for recording image information on the solid-state radiation detector is performed. The image signal, which has been outputted from the solid-state radiation detector having been subjected to the operation for recording the image information, is corrected in accordance with offset information, which is constituted of the high frequency offset component information and the low frequency offset component information. The image signal is thus capable of being corrected quickly and accurately such that offset components are removed from the image signal.