A light-emitting device according to an embodiment comprises: a substrate; a first buffer layer disposed on the substrate; a second buffer layer disposed on the first buffer layer and containing Al; a first conductive type semiconductor layer disposed on the second buffer layer; an active layer disposed on the first conductive type semiconductor layer; and a second conductive type semiconductor layer disposed on the active layer, wherein the second buffer layer comprises a first layer and a second layer which are horizontally disposed, the first layer having an increased Al composition ratio as the first layer becomes closer to the first conductive type semiconductor layer, and the second layer having an decreased Al composition ratio as the second layer becomes closer to the first conductive type semiconductor layer. The embodiment configures the buffer layer by horizontally disposing the first layer of which the Al composition ratio linearly increases and the second layer of which the Al composition ratio linearly decreases, thereby having an effect of being capable of effectively controlling strain due to the lattice mismatch and the thermal expansion coefficient difference between the substrate and the first conductive type semiconductor layer.