The present invention discloses a communication device with an adjustable brightness that includes a control circuit coupled to a modulating unit, and the modulating unit includes a tuning button disposed on the communication device that allows user to make adjustments or controls by the tuning button to produce a first set value, and the modulating unit converts the power received by a power supply circuit of the communication device into a corresponding operating voltage according to the first set value and sends the operating voltage to a light emitting unit of the communication device for projecting a light source according to the magnitude of the operating voltage, so as to adjust and change the brightness of the light emitting unit, and achieve the effects of saving power and extending the life of the light emitting units.