To perform turning, flattening, grooving, and machining of an inclined small diameter hole and a deep hole on the same machine by providing a technical means for highly accurately machining the deep hole having a small diameter by using a rotary tool such as a drill installed in a lathe.

One of a toolpost is a turret toolpost 5, and the other is a turret toolpost having a rotary tool driving shaft or a toolpost 4 mounted with a rotary tool driving device turnable around the Y axis. A rotary tool 8 is installed in the turret 4a toolpost having the rotary tool driving shaft or the rotary tool driving device. A guide block 9 having an axial directional guide bush 11 of the rotary tool 8 is installed in the other turret toolpost. The guide bush 11 is brought near to a boring position of a work 3 gripped by a main spindle, and the rotary tool 8 is guided by the guide bush 11 to perform boring machining.