To provide a method for machining a fine hole tilted by a required angle on the workpiece made of relatively hard material, which method can form the fine hole having a furthermore large tilting angle and a furthermore large depth, and further can achieve the shape accuracy and the positional accuracy of a high level.

In the method for machining a tilted fine hole, the fine hole is drilled such that the rotary axis of a drill is aligned with the expected drilling line X tilted with respect to the normal line for the surface of a workpiece 1, and the drill is fed with a required feed pitch. In this case, a guide hole 10a, which has nearly the same inside diameter as the diameter d of the drill, and suppresses the run-out of the rotary axis of the drill in the radial direction by holding the tip end portion of the drill, is provided by nearly cylindrically cutting the surface of the workpiece 1 using an end-mill 2 such that its central axis coincides with the expected drilling line X. Then the tip end portion of the drill 30a is inserted into the guide hole 10a, and the drilling process is started. Thus, the drilling position and the drilling direction are made so as to coincide with those of the expected drilling line X by guiding the drilling position and the drilling direction by means of the guide hole 10a in the approaching stage of the drilling work.