When an X-ray detector is removed from a storage part, a sensor senses this, and transmits to an up and down control part a signal indicating that the X-ray detector has been taken out of the storage part. Upon receipt of the signal, the up and down control part releases braking force by electro permanent magnets. In doing so, sticking force of the electro permanent magnet on a fixing part, and sticking force of the electro permanent magnet on a stopper plate are released. The weight of a counter weight is larger than the total value of the weights of the arm, X-ray tube, collimator, and the like, and therefore in a state where the arm is released from being fixed by the electro permanent magnets, the arm starts to move up together with the X-ray tube and the collimator.
