PURPOSE: To accurately calculate the chill depth and necessary inoculation amount of the original molten metal.

CONSTITUTION: A wedge-shaped chill container 10 cooling the original molten metal, the thermocouple 20 arranged to a part generating no chill and detecting the temp. of a molten metal, cooling curve measuring means 31, 37, 32, 33 measuring the timewise change of the temp. of the molten metal, characteristic point detection means 32, 33 detecting primary crystal temp., supercooling temp. and eutectic temp. from a cooling curve, chill depth operation means 32, 33 operating the chill depth of the original molten metal on the basis of primary crystal temp., supercooling temp. and eutectic temp. and a chill depth display means 36 displaying chill depth are provided. Further, a characteristic storage means 33 storing the relation between the chill depth of the original molten metal and an inoculation amount after inoculation using chill depth as a parameter, an inoculation amount operation means 32 operating the inoculation amount corresponding to the chill depth of the original molten metal operated using the characteristic selected from the characteristics stored in the characteristic,y' means corresponding to the desired chill depth after inoculation and a display means 36 displaying an inoculation amount are provided.