The problems of solidification in the mold of continuous casting cause q break-out, and w Surface defects. Daido Steel has installed Mold Solidification Condition Detecting System at No.1CC in Chita Plant to get the correct solidification condition in the mold and to encounter them adequate-ly. The following are the results that we got in the development period. (1) Sticking break-out can be detected correctly by the on-line judging system using neural network and the learning system. (2) We can prevent break-out by reducing casting speed with the alarm system which is associated with the judging system. (3) We can also detect the depressions on the bloom surface, and on-line judging of the bloom surface quality can be performed. We will connect the bloom quality information to the on-line judging system for conditioning method in the future. (4) It is possible to detect longitudinal cracks which are accompanied with depressions with use of the above system, but it is found out to be difficult to detect them at the position far more than 30 mm from the measuring point. To