A light-emitting element comprises a light-emitting stack comprising an active layer for emitting a light; a window layer on the light-emitting stack; and a first insulative layer having a first refractive index on the window layer; wherein the first insulative layer has a first refractive index, and the window layer has a second refractive index, and a difference between the first refractive index and the second refractive index is larger than 1.5.