A light emitting diode includes a substrate, a first semiconductor layer, an active layer, a second semiconductor layer, a first optical symmetric layer, a metallic layer, and a second optical symmetric layer stacked on the substrate in that sequence. A first electrode is electrically connected to the first semiconductor layer, and a second electrode is electrically connected to the second semiconductor layer. A first effective refractive index n1 of the second optical symmetric layer, a second effective refractive index n2 of an integrated structure satisfy |n1−n2|≦0.5, wherein the integrated structure includes the substrate, the first semiconductor layer, the active layer, the second semiconductor layer, and the first optical symmetric layer.