An X-ray detector that is detachably mountable in a mounting unit, the detector comprises a storage unit configured to store identification (ID) information, which is assigned to the X-ray detector according to its usage, of the X-ray detector, a position detecting unit configured to detect a mounting position information of the X-ray detector and a communication unit configured to transmit the mounting position information of the X-ray detector and ID information of the X-ray detector to a workstation.