There is provided a deep hole processing device for forming a hole by rotational movement of a main spindle to which a tool is attached of a portal machine toward a workpiece, having, a bush having a hole diameter for guiding rotational movement of the tool, and a bush holding unit provided on a cross rail capable of moving on columns of the portal machine for holding the bush with respect to a spindle head on which the main spindle is mounted at a predetermined distance, wherein a position of the bush relative to the workpiece and a pressure at which the bush is pressed against the workpiece may be controlled by movement of the cross rail.