To shorten an adjusting work time and to improve obstacle sensing accuracy in a mounting structure of an obstacle detector for an opening/closing device that can easily adjust the position of an obstacle sensor with high accuracy.

The mounting structure of the obstacle detector for the opening/closing device is provided for mounting detector to a pair of guide rails 27 comprising groove members for guiding both side edge parts 13a of an opening/closing body 13, and outer frames for fixing the groove members to a building skeleton. The mounting structure is provided with support members fixed to the inside of the outer frames; lateral swing frames turnably supported to the support members; vertical swing bases turnably supported to the lateral swing frames; the sensing means fixed to the vertical swing bases and arranged in openings bored in the outer frames; lateral adjusting means capable of changing the holding positions of the lateral swing frames to the support members; and vertical adjusting means capable of changing the holding positions of the vertical swing bases to the lateral swing frames.