An X-ray detector to make possible digitization of an existing X-ray imaging apparatus is to be realized. Also an X-ray detector excellent in versatility is to be realized. This is an X-ray detector having a flat panel type detector unit for detecting the two-dimensional intensity distribution of incident X-rays and an interface unit for a detection signal utilizing device, and the interface unit conforms to open standards regarding images for medical use and communication. The interface unit has a first node on the detector unit side, a second node on the detection signal utilizing device side and a network linking them. The network is the Ethernet. The first node and the second node perform communication conforming to TCP/IP. The first node is integrated with the detector unit. The open standards regarding images for medical use and communication are the DICOM standards.