Provided is an apparatus for detecting opening and closing of a door. The apparatus includes a sensor unit, which is installed at a location close to a first member and detects an opening and closing of a door, a loading unit coupled to the sensor unit and a folded unit, folded and rotated based on a center of the folded unit when a back set distance from a side surface of the door to a center line of an indoor unit is small, and led in an installation groove of an indoor unit, and a case coupled to the loading unit when the back set distance from the side surface of the door to the center line of the indoor unit is larger, and separated from the loading unit when the back set distance from the side surface of the door to the center line of the indoor unit is small.