A failure diagnosing method of logic circuits includes generating failure candidate data for logic circuits based on failure diagnosis data obtained from the logic circuits by using a failure diagnosis tool; and inputting the failure candidate data for the logic circuits. A predetermined data is extracted from each of the failure candidate data for the logic circuits. Failures of the logic circuits are diagnosed by collecting a name of each of the failure candidate data from the predetermined data and the number of failure candidate data; and the collected data are outputted on a display unit.