To provide an obstacle detecting device resulting in a winding quantity of fewer cords, even if a dimension of the opening height increases, in a cable type obstacle detecting device using a cord reel.

The lower end side of the cord 11 for transmitting an obstacle detecting signal, is connected to a seat plate switch 3 in a position biassed in the opening width direction to a position just under a cord winding part of the cord reel 10, and the cord 11 is put in a state of extracting by the predetermined length when fully opening an opening part. The cord reel 10 has an energizing means in the winding direction of the cord 11. The cord 11 is wound or extracted in a state of extending in an inclined shape in the moving direction of a shutter curtain 2.