A server includes a rack, at least one server unit, at least one communication exchange unit, at least one rack control unit and an electric power transmission unit. The rack has a plurality of shelving spaces. The server unit, the communication exchange unit, and the rack control unit are moved into or moved out of a corresponding shelving space along a horizontal axis, respectively. The server unit is communicatively connected to the communication exchange unit, and communicates with the rack control unit through the communication exchange unit. The electric power transmission unit is disposed in the rack and runs adjacent to the shelving spaces along a vertical axis. After the server unit, the communication exchange unit and the rack control unit are moved into corresponding shelving spaces, the server unit, the communication exchange unit and the rack control unit are electrically connected to the electric power transmission unit.