A light-emitting device is disclosed and comprises: a transparent substrate; a semiconductor light-emitting stack on the transparent substrate, wherein the semiconductor light-emitting stack comprises a first semiconductor layer close to the transparent substrate, a second semiconductor layer away from the transparent substrate, and a light-emitting layer capable of emitting a light disposed between the first semiconductor layer and the second semiconductor layer; and a bonding layer between the transparent substrate and the semiconductor light-emitting stack, wherein the bonding layer has a gradually changed refractive index, and each of critical angles at the bonding layer and the transparent substrate for the light emitted from the light-emitting layer towards the transparent substrate is larger than 35 degrees.