Provided is an apparatus or a method that can stabilize flight of an unmanned aerial vehicle after package receiving or package passing. A port as a package receiving or passing apparatus includes: a landing portion on which an aerial vehicle lands; a slider for horizontally moving the landed aerial vehicle to an indoor area; an elevating/lowering portion on which a package-chamber tray taken down from the aerial vehicle in the indoor area is to be placed; a movement control portion for elevating/lowering an elevating/lowering portion; a package moving portion for moving a package between a package storage portion and the package-chamber tray placed on the elevating/lowering portion; and a center of gravity adjustment portion for adjusting the center of gravity position of the aerial vehicle after package receiving or package passing.