A light-emitting device is provided. The light-emitting device generates a white light and includes at least one light-emitting diode. The at least one light-emitting diode generates a light beam with a broadband blue spectrum and includes a first semiconductor layer, a second semiconductor layer and a multiple quantum well structure. The multiple quantum well structure is located between the first semiconductor layer and the second semiconductor layer, and includes well layers and barrier layers. The well layers include a first well layer, a second well layer and third well layers different in indium concentrations. The first well layer has the largest indium concentration, and the third well layers have the smallest indium concentration. Three of the well layers that are closest to the first semiconductor layer are the third well layers, and the first well layer is closer to the second semiconductor layer than the first semiconductor layer.