PURPOSE: To provide a device with high rigidity and accuracy by enabling a turret head to be subjected to arbitrary interrupting indexing and subjected to milling while utilizing a motor for main shaft driving.

CONSTITUTION: On a shaft head body 10 movably guided by a slide base as a column 12, a cylinder 20 is bored concentrically with respect to the rotary axis of a turret head 11, and a central boss part 23 of the turret head is supported with a bearing on a piston rod 22. At the turning position of a rocking lever 60, a clutch element 34 is shifted in the right direction, disconnected from a rotary main shaft 13a, allowed to be coupled to an intermediate shaft 44 for indexing, since a clutch lever 56 is turned by an angle α. Under this condition, the turret head 11 is subjected to rotary indexing by turning the main shaft motor in normal and reverse direction. At this time, the piston 21 of the cylinder 20 is lifted to carry out indexing in a state where an engagement between coupling gears 26, 27 is off, and after completion of indexing, the piston 21 is lowered, allowing the coupling gears 26, 27 to be engaged and clamped.