The invention provides a boring mill. The boring mill comprises a base, a support, a boring bar driving device, a boring bar and a boring cutter, wherein the liftable support is located on the base, the boring bar driving device is located in the support and is connected with the boring bar, and the boring bar is connected with a boring bar lengthening device. The boring mill is characterized in that the boring cutter is located on the boring bar lengthening device, a locating bearing is arranged on the boring bar, and the base is provided with a limit mechanism; a bearing is arranged on the boring bar, the locating bearing is placed in a formed hole when an axial hole is processed, the boring bar is located, and the vibrating can be reduced in the processing process, so as to improve the processing precision of a coaxial hole; the limit mechanism can be arranged to ensure the relative positions of the boring mill and a to-be-processed work-piece, the relative displacement between the work-piece and the boring mill can be prevented, and the processing precision of the coaxial hole can be improved.