PURPOSE: To simplify the constitution and shorten the indexing time by engaging the gears of both a tool spindle and a motor with each other by the clamping action, disengaging there gears by the unclamping action, and selectively executing the process revolution and the indexing revolution with a single motor.

CONSTITUTION: When an indexing command is issued, liquid is fed into a pressure chamber 19b so that a turret head 8 is separated from a main body 7, curvic couplings 23 and 24 are detached from said head 8, a spindle gear 16 is disengaged from a gear 29, the notch 62 of a stopper 55 is engaged in a supplementary stopper 56, each of tool spindles 13 is restricted from being turned and held in the normal position by an engaging part 57 to become unclamped. When clutches 46 and 47 are, at the same time, engaged with each other and the motor 32 is turned, a turret head 8 is indexed via a worm gear 38 and gears 31 and 22 and the angle of revolution is detected by a rotary encoder. Then fluid is fed into a pressure chamber 19a, the turret head 8 goes near the main body 7, the couplings 23 and 24 are engaged, and the spindle gear 16 in the indexed position P is also engaged with the gear 29. The flange of a stopper 55 is separated from the supplementary stopper so that the revolution of the tool spindle 13 is allowed to be turned.