Abstract: An index head provided with a long rack and a short rack which are slided alternatively towards an index table by the movement of a pinion of a piston rod. The long rack which is characterized to move at a speed twice a forwarding speed of the piston rod, gives to the index table a revolution corresponding to desired divisions. Immediately upon the completion of said revolution of the index table, the short rack which becomes then movable at a speed twice the forwarding speed of the piston rod, brings about, in cooperation of the rotary movement of the pinion, the engagement of the piston rod with the index table, whereby inertia given to the index table through its revolution by the long rack is prevented so as to attain accurate divisions.