A portable X-ray detector includes: a detection panel having an incident surface defined on a front surface thereof facing a generator and configured to generate an electrical signal for each position which is proportional to an incident amount of X-rays generated from the generator; a backing housing detachably fixed to a rear surface of the detection panel and having a sealed mounting space defined therein; and a communication module mounted in the mounting space and configured to wirelessly transmit the electrical signal generated from the detection panel.