To provide an opening section device having a simple structure and a high convenience without mounting a locking device on a door body.

The opening section device 1 has frame bodies 10 mounted along the four sides of a building opening section and wing frames 15 arranged in the frame bodies. The opening section device 1 further has door bodies 20 arranged on the insides surrounded by the frame bodies and the wing frames and the locking devices 30 and 30 enabling a locking and an unlocking by engaging and disengaging the wing frames and the door bodies. In the opening section device 1, operating sections for the locking devices are mounted on the wing frames.