A server device includes a server rack and at least one server unit having a first sliding tray, a second sliding tray, a storage array module and a motherboard module. The server rack includes a first opening and a second opening which are opposite with each other. The first sliding tray is slidably disposed in the server rack. The second sliding tray is slidably disposed in the first sliding tray. The storage array module is disposed on the second sliding tray. The motherboard module is disposed on the first sliding tray and electrically connected to the storage array module.