A radiation detecting cassette includes an IC card detector which detects insertion of an IC card in a slot, outputs a detection signal representing that the IC card is inserted in the slot, and reads ID information stored in the IC card. An ID checker of the radiation detecting cassette checks the ID information against ID information stored in a card ID memory. A power unit controller controls supply of electric power from a power unit to a radiation detector and/or components of the radiation detecting cassette based on a checking result from the ID checker.