There is provided an apparatus for an automatic/semiautomatic door, and more particularly, to an apparatus for an automatic/semiautomatic door to prevent the door from leaving its track during an opening/closing process and to maintain airtightness between the inside and the outside when closed. In the apparatus for the automatic/semiautomatic door, airtight frames are separably assembled at the top, bottom and both sides of the automatic/semiautomatic door and wherein an airtight structure is buried in a floor surface coming in contact with the bottom of an opening/closing door of the automatic/semiautomatic door, so that the airtight frame is air-tightly and slidably inserted into the airtight structure. Therefore, any gap between the inside and outside is blocked to improve airtightness by preventing drafts, noise, etc. and the opening/closing door is prevented from shaking or leaving its track.