A data center includes a container, a server system, an air conditioner, and an air guide. The container includes a floor, and a sidewall that defines a through hole adjacent to the floor. The server system includes a rack and a number of servers mounted in the rack. The rack defines an air outlet apart from but facing the sidewall. The air conditioner includes an evaporator and a condenser. The evaporator is positioned on the top of the rack. The condenser defines an outlet and is sandwiched between the bottom of the rack and the floor and extending through the through hole. The air outlet of the condenser faces outside of the container. The air guide is a sheet extending from an edge of the evaporator that is distant from the rack and then bends to extend toward the floor.