To detect an obstacle so as to prevent a wafer carrier from colliding on it by providing an obstacle detection sensor for detecting the existence of obstacle by the application of optical search in an elevation path between a carriage with a hoist and a load port of each production device, at the side of carriage.

A carriage 3 with a hoist is provided with an obstacle detection sensor 22 for detecting existence of an obstacle 21 through the application of optical search in an elevation path beween the carriage 3 and a load port 8 of each semiconductor production device 7. With the sensor 22 provided to the side of the carriage 3 with the hoist the number of which is less than that of the devices 7, a wafer carrier at the time when it is hung is prevented from colliding on an obstacle 21 such as a worker or a carelessly placed substance by detecting it before hand.