PURPOSE: To perform position adjustment in the direction of an axial line after positioning of a work is performed, in the captioned device performing the positioning on the basis of an internal hole of the work, by lifting a main unit of the work positioning device.

CONSTITUTION: A bush 33 is mounted to a round hole 34 in a jig base 32, and a main unit 35 of a machine tool work positioning device is slidably inserted into the bush 33. A rack 36 is formed to the main unit 35 and engaged to a driven union to constitute a main unit moving means. The first wedge member 39 is slidably fitted to a bore 40 of said main unit 35, and the second wedge member 49 is slidably inserted into a through hole drilled in an upper end part of the member 39. An eccentric cam main unit 64 is formed to one end part of a cam shaft 61, supported to said member 39, and the first and second wedge members 39, 49 are mutually relatively moved by action of the cam 64, then the first and second location pins 45, 54 are pressed by the wedge members and simultaneously protruded to perform positioning of a work 4.