A server rack and its server device are provided. The server device includes a chassis, a motherboard module, a power-supply module, a storage array module, and a plurality of input/output interface elements. The chassis is provided with a containing space, a first opening and a second opening in which the first opening and the second opening are located at two opposite ends of the containing space. The power-supply module and the motherboard module are both disposed in the containing space and are pluggable independently, are both capable of plugging in and out from the chassis via the first opening, and are electrically connected to each other. The input/output interface elements are fixed on the motherboard module, and all of them are disposed at the first opening. The storage array module is disposed in the containing space and is slidable.