A height sensor 26 and an image recognizing section 28 are installed in a teaching unit 24; the height sensor 26 contacts a pin 30a on a load port 4 to detect the height position of the pin 30a and the image recognizing section 28 recognizes a pin 30c and thus its horizontal plane position. A platform 16 of an overhead travelling carriage 8 grips and lowers the teaching unit 24 toward the load port 4. The height sensor 26 then detects the height of the load port 4. Then, the teaching unit 24 is slightly raised. The horizontal plane position of the pin 30c is recognized and averaged over a time equal to at least the vibration period of the platform 16. As a result, the position of the load port can be accurately taught to the overhead travelling carriage 8 without preparations such as the installation of marks on the load port.