Abstract: A continuous casting process introduces the factor of rate temperature change for detecting break out in the cast metal. Introduction of rate of temperature change as a parameter representative of the cast metal condition is successful for avoiding the influence of variation of the casting condition, fluctuation of the powder to be introduced between the casting mold wall and the cast metal, casting speed and so forth. For achieving accurate detection of break out of the cast metal by introducing the temperature change factor, casting mold wall temperatures are measured at various measuring points which are circumferentially aligned. Rates of temperature change at each measuring point and average rate of temperature change of all measuring points are derived and compared for making judgement of possible break out when the difference of the rate of temperature change at each measuring point and the average rate of temperature change becomes greater than a predetermined value.