PURPOSE: To intend more safety by providing an object detector at a connection port between an automatic warehouse the circumference of which is enclosed for any body not to enter and the outside, so that the detector may be invalidated when loadings pass through and otherwise a stop signal can be output.

CONSTITUTION: Beam sensors 30-33 are provided at a connection port between an automatic warehouse and the outside to detect objects which pass through for inputting to a control device. That means, if a light receiver 30b for the beam sensor 30 detects obstacles, an emergency stop signal is output to stop a conveyor 22, a stacker crane, etc.. When the beam sensor 32 is activated, an obstacle detecting signal from the light receiver 30b is invalidated and kept in an invalidated condition until the beam sensor 33 at a rear step is activated. In this way, better safety is intended.