A light emitting device including a voltage source, a light emitting unit, and a current source is provided. The voltage source is coupled to the light emitting unit for supplying a voltage. The light emitting unit includes n light emitting diodes (LEDs) and n current control switches, wherein n is greater than or equal to 3. The LEDs are respectively coupled to the current control switches in series. The current control switches are turned on and off according to a current threshold. The current source is coupled to the light emitting unit for supplying a fixed current. Thereby, the luminous intensity of the light emitting device remains stable even when some of the LEDs fail.