Disclosed is a method and an apparatus for testing an optical fiber by using a biorthogonal codes and a Moore-Penrose inverse matrix. The method includes the steps of: (a) coding 2n optical pulses according to each codeword of the n-bit biorthogonal code matrix (2n*n matrix), injecting the coded optical pulses into an optical fiber, and measuring 2n optical signals generated when the coded optical pulses are reflected from the optical fiber; (b) decoding the 2n optical signals measured in step (a) by means of the Moore-Penrose inverse matrix (n*2n matrix) for the n-bit biorthogonal code matrix, thereby restoring n signals; (c) shifting the n signals along the time axis to remove timing differences among the n signals; and (d) performing an average operation for the time-shifted n signals and obtaining a final measured value.