Provided is an apparatus determining values of N and K for an abnormality diagnostic logic which makes a diagnosis N times for each diagnosis target by using observation values collected therefrom, and generates a diagnosis result showing that the diagnosis target is abnormal if the diagnosis target is judged to be abnormal K or more times. A calculator calculates average false detection rate PFP, average overlooking rate PFN, bias level of false detection MFP, and bias level of overlooking MFN, based on diagnosis result data and inspection result data. A determiner calculates an optimization metric for each combination of values N and K by using the average false detection rate, the bias level of false detection, the average overlooking rate, and the bias level of overlooking, and selects a pair of N and K by which the optimization metric becomes minimum or a threshold value or less.