The invention discloses a numerical control lathing outer cylindrical face vertical hole positioning bending plate device and positioning method, and belongs to the technical field of machining. The problems that when outer cylindrical face vertical holes are machined, centers of two vertical holes need to be aligned twice, the production efficiency is low, and the device and method are not suitable for batch machining are solved. A positioning pin and a positioning shaft are arranged in parallel, a center hole is formed in a back plate, and a first positioning assembly and a second positioning assembly are mounted on a supporting plate; when a first to-be-machined hole is machined, a machined cylindrical workpiece is mounted on the first positioning assembly, a first positioning hole is matched with a first positioning pin, a second positioning hole is matched with a first positioning shaft, and the axis of the first to-be-machined hole coincides with the axis of the center hole of the back plate. When a second to-be-machined hole is machined, the machined cylindrical workpiece is mounted on the second positioning assembly, the first positioning hole is matched with a second positioning pin, the second positioning hole is matched with a second positioning shaft, and the axis of the second to-be-machined hole coincides with the axis of the center hole of the back plate. The device is simple and practical in structure, and the manufacturing cost is low.