Appropriate calibration is provided when a radiographic image is taken using a radiation detector. When a detecting unit (40) detects at least one of conditions including that power is applied to cassettes (22A, 22B), that a predetermined time period has elapsed from the application of power, and that the cassettes (22A, 22B) are connected is detected, a control unit (48) determines whether or not calibration information of the currently connected cassettes is appropriate. If a negative determination is made, calibration is carried out to obtain new calibration information.
