A feedback device for a constant current driver controls a power supply module in the constant current driver to generate an output voltage. The constant current driver drives an electrical load with an output current. The feedback device includes a feedback control module and a feedback output unit. The feedback control module is utilized for receiving a load driven voltage related to the electrical load and generating a control voltage accordingly. The feedback output unit is utilized for generating a feedback current via an equivalent resistor of the feedback output unit according to a voltage difference between the control voltage and a feedback voltage of the power supply module. The power supply module controls the magnitude of the output voltage according to the feedback current, allowing the constant current driver to drive the electrical load with the output current.