The present invention provides a light-emitting device and a manufacturing method thereof. The light-emitting device includes: a heat dissipation layer (2), a buffer layer (4) formed on the heat dissipation layer (2), and a light emission unit (6) formed on the buffer layer (4). The heat dissipation layer (2) is made of graphene. The manufacturing method of a light-emitting device according to the present invention makes use of a graphene-made heat dissipation layer to effectively dissipate away heat emitting from the emissive layer of the light emission unit so as to effectively reduce the temperature of the light-emitting device and extend the service life of the light-emitting device. Particularly, when the light-emitting device is a light-emitting diode, the emissive layer thereof is a quantum dot emissive layer for effectively improving color saturation of the light-emitting diode and enhancing color displaying performance of the light-emitting diode.