A machine tool is equipped with a rotary table, and a clamp mechanism which clamps the rotary table in a manner so that the rotary table does not rotate. A clamping operation by the clamp mechanism is started after a standby time has elapsed from completion of indexing of the rotary table. The machine tool further includes a positional deviation calculating unit adapted to calculate a positional deviation of the rotary table when the clamping operation by the clamp mechanism is completed, and a standby time changing unit adapted to shorten the standby time in the case that an absolute value of the positional deviation is less than a threshold value, and to lengthen the standby time in the case that the absolute value of the positional deviation is greater than the threshold value.