To enhance the obstacle detecting sensitivity of an elevator door by analyzing a detector signal to determine the cutting-off of beams discharged from a plurality of emitters, and providing a means for executing variable threshold value detection.

An emitter array 25 is provided in a first door 20, and a detector array 30 is provided in a second door 15. A controller 35 is installed in the uppermost part of an elevator car 10, and electrically connected to both of the emitter array 25 and the detector array 30. An electrical link 55 functions such that the controller 35 operates the emitter array 25 and the detector array 30 in cooperation with each other. Thus, by variably controlling a detection threshold value, obstacle detecting sensitivity in a defined region such as an elevator car door way or the like is enhanced, and even if the doors approach each other, a very small obstacle or a translucent obstacle in a gap between the doors is detected.