Provided is a mobile X-ray imaging device having a foldable arm unit equipped with an X-ray tube unit, and a storage concave for storing the folded arm unit on the front side of a main body. An end of the arm unit fixed to the main body side is made slidable with respect to the main body. With this configuration, it is possible to provide the mobile X-ray imaging device having a high degree of flexibility in arranging the X-ray tube when imaging is performed, and also the forward view is never be obstructed by the device in transit.