To provide a positioning device by which a manipulator can be accurately positioned without performing initial positioning.

Laser beam sources 14 and 16 to emit first and second reference beams crossing each other at a prescribed first point and laser beam sources 15 and 17 to emit third and fourth reference beams crossing each other at a prescribed second point, are arranged in a robot, and when plural light sensors provided in respectively different positions of a positioning part 20 installed in a prescribed position of a manipulator 1 detect prescribed one in the first or the fourth reference beam, a control part 2 calculates a turning angle of a motor on the basis of an axial angle of a joint.