PROBLEM TO BE SOLVED: To provide a surface defect determination method and apparatus for a slab manufactured by continuous casting and a manufacturing method for a steel cast piece using them.SOLUTION: A surface defect determination method for a continuous casting slab related to this invention includes the temperature measurement data acquisition step of disposing a thermocouple 5 embedded in a casting mold 3 so as to satisfy a predetermined installation range, gap, etc. with respect a casting direction and a casting mold width direction to acquire a temperature of a casting mold copper plate with the disposed thermocouple 5, the main component analysis step of grouping the acquired temperature measurement data into two or more groups to calculate a main component score by main component analysis for each of the groups, and the main component score determination step of determining the generation of defects in a slab surface for each of the groups on the basis of the calculated main component score.SELECTED
