To provide an indexing device for a machine tool manufacturable simply and inexpensively and having high rigidity to prevent heat generation accompanied with operation of the indexing device.

In this device provided with an indexing table 2 for the machine tool supported rotatably at a fixed position by a bearing 4 and rotated minutely by an ultra-precision indexing mechanism 5 and a rotation on-off controller 6 fixing the table to a rotation position in an immobile manner, the rotation on-off controller is composed of an annular fixed rack 8 fixed to outer periphery of the table and an annular movable rack 9 provided on the table so as to elevate freely and prevent its rotation and meshing with the fixed rack so as to engage and disengage freely. Elevation of the movable rack is performed by a lever capable of swinging freely, and the table and the fixed rack are used for outer and inner of the bearing.