Abstract: Waveform diagrams of cholesterol and triglyceride, for example, obtained by electrophoresis are overlappedly displayed (superimposed). To compare or overlappedly display two waveform diagrams, one unit of absolute concentration is related to one unit of waveform size for normalization. With this method, phenotype classification of lipid can be easily performed. Further, phenotype can also be performed quantitatively and automatically from two waveform diagrams. Thus, a plurality of waveform diagrams of lipid in serum (plasma) obtained by a densitometer or the like can be quantitatively compared.