An acceleration sensor is installed in an electronic cassette. The acceleration sensor detects a shake. When magnitude of the shake, measured using the acceleration sensor, is greater than or equal to a shake detection threshold value, a judging circuit of a shake detecting section turns off a switching element. An operation switching section is disconnected from an irradiation detecting section that detects a start of X-ray irradiation. Thus, an irradiation detection function of the irradiation detecting section is disabled. After a predetermined time, the judging circuit outputs an ON signal to the switching element to turn on the switching element. Thereby, the irradiation detecting section resumes the irradiation detection.
