An integrally formed multi-layer light-emitting device is provided, which includes a seat, a plurality of light-emitting elements, and two lead frames. The seat is integrally formed in such a manner that the light-emitting elements can fit in the chamber which is formed on the top portion of the central main body. The seat is made of metal, and thereby the seat can effectively absorb heat from the light-emitting elements, and rapidly transmit it to the surrounding environment. Therefore, the packing module is not needed to be used in the present invention so that the consumption of the package material is reduced, and the manufacturing process is simplified.