A system is in a standby mode as an imaging preparation condition in step S1. If gripping of an operation handle is detected in step S2, the operation goes to step S3, in which an electromagnetic brake is released and thereby allowing a radiation detector to be rotated substantially around the center of an imaging region. If a rotation angle is detected in step S5 and a first limiting device covering an effective imaging region of the radiation detector is changed to a second limiting device so as to be constantly arranged within the effective imaging region even during rotation of the radiation detector.
