An apparatus for testing a back light unit is provided to integrate a signal generator for generating a test signal with a power supply unit to test an automatic color calibration function rapidly and easily, thereby improving productivity. An apparatus for testing a back light unit includes a power supply unit(110) and a signal generator(100). The power supply unit supplies power to an LED(Light Emitting Diode) back light unit. The signal generator generates an IIC(Inter IC) signal for controlling the LED back light unit. The power supply unit includes a switching mode power supply. The signal generator includes a microcomputer(102) for generating the IIC signal and a memory(104) for storing predetermined data. The apparatus further includes a switching unit(120) for controlling the power supply unit and the signal generator. The apparatus further includes a first connector(130a) for connecting the power supply unit to the LED back light unit and a second connector(130b) for connecting the signal generator to the LED back light unit.
