An electronic device having an expansion interface includes a shell, a button, a circuit board, switch and a voltage adjusting unit. The shell defines a through hole. The button is movably received in the through hole. The button includes a first electroluminescent portion and a second electroluminescent portion. The switch is electrically connected to the circuit board and is activated by the button to control whether to load a same voltage to the first electroluminescent portion and a second electroluminescent portion to drive them to emit light of equal brightness. The voltage adjusting unit changes the voltage loaded to the second electroluminescent portion to drive the second electroluminescent portion to emit light having a different brightness from the light emitted from the first electroluminescent portion when an expansion device is connected to the expansion interface.