A rack device having a cabinet and power modules stacked in the cabinet is provided. The power module has a frame, an insulative plate, an insulative cover and transformers. The insulative plate is arranged in the frame. The insulative cover is arranged in the frame and disposed spacedly from and parallel with the insulative plate. Each transformer arranged in the frame has a high-voltage set and a low-voltage set electrically connected with each other. The low-voltage sets are arranged on one surface of the insulative plate and do not protrude from the frame, and the high-voltage sets are arranged on another surface of the insulative plate and between the insulative plate and the insulative cover. The frame of each power module is connected with the frame of adjacent power module, and the frame of at least one of the power modules is connected to the cabinet.