A method and an apparatus which adjusts a signal read from an optical disc in order to obtain stable binary data. The signal adjustment method comprises (a) detecting a period of an input signal of a predetermined code; (b) determining whether the detected period is smaller than a predetermined value; and (c) if the detected period is determined to be smaller than the predetermined value, adjusting the input signal so that its period equals the predetermined value, and outputting the input signal. The signal adjustment method and apparatus of the present invention reduce errors and improve system performance, when a signal input to the binary processor does not meet its code feature.