A method for evaluating reproduced signal wherein when Euclidean distance is calculated by judging the coincidence between a binary bit array and a predetermined evaluation bit array in the evaluation of the quality of reproduced signal, in a large capacity optical disc system with constraint length equal to or greater than 5, the assumption is made that the continuous 2T count included in a predetermined evaluation bit array is denoted by i and that each evaluation bit array is composed of a main bit array having a bit length of (5+2i) and auxiliary bit arrays added before and after the main bit array; judgment on whether binary bit arrays include the predetermined evaluation bit array, is concentrated on the coincidence judgment of the main bit arrays; and at the same time, the Euclidean distance between the reproduced signal and the target signal corresponding to the evaluation bit array is calculated with respect to each main bit array and the results of such calculations are separated and counted.