A server includes a casing, a frame, at least one movable carrier and at least one M.2 expansion card. The casing has a through hole. The frame has an opening and an accommodation space connected to the opening. The frame is fixed in the casing and the opening corresponds to the through hole, so that the accommodation space is exposed to exterior via the through hole. The at least one movable carrier is removably disposed in the accommodation space, and the at least one M.2 expansion card is disposed on the movable carrier.