A power plug device includes a first housing, a circuit board, a wire assembly and a second housing. The first housing includes an upper-housing body, a through hole and an inner cover. An accommodating portion is arranged in the upper-housing body, the through hole is formed on one side of the upper-housing body, the inner cover is installed in the accommodating portion, a receptive space is arranged in the inner cover, and the through hole interconnects with the receptive space. The wire assembly includes core wires, which passes through the through hole and the receptive space, so that the core wires are accommodated in the accommodating portion, and the receptive space is suitable for accommodating glue to secure the core wires and provides waterproof effect. In addition, dual-layered waterproof structure is used to make the first and second housing joining together having stronger waterproof effect.