An apparatus and a method for compensating an error of an AQM measuring and compensating the error using returned I/Q digital signals calculate the error compensating signal is disclosed. The process includes detecting a DC offset signal by averaging sampling values of returned I/Q digital signals; detecting a gain compensating signal using a maximum value in a period of the I/Q digital signals of which the DC offset is compensated; and detecting a phase compensating value of the I/Q digital signals on the basis of sum of absolute values for differences between the gain compensated I-digital signals and Q-digital signals, and remove phase error, gain error and DC offset of the inputted digital signal sequentially to compensate the AQM error. |