To provide a positioning device at a low cost which can attain a simple structure and shorten work transferring time.

An L-direction positioning plunger having a contact head 2 energized by a coil spring 5 is fitted on a robot hand 30 operated by a robot 20. A work W is pushed by a head 2 together with the advance of a hand, and pressed against the protruding streak 12 of a cassette 10 to determine a position in the L-direction automatically. The position in the B-direction is determined by width aligning mechanism 60. This can eliminate need for fitting a station having a two-axle positioning device in its intermediate position, thus it is possible to shorten transferring time, simplify the device and attain cost reduction.