At each of measurement sites, changes in plural biological data (such as an oxy-Hb signal species and a deoxy-Hb signal species) in a predetermined period are statistically tested independently of each other. By combining results of the plural biological data, the measurement sites are each classified into one out of plural categories. The classified results are each displayed in a single chart. Effective is also a method of setting different activity periods correspondingly to plural Hb signal species, deciding whether or not each of the signal species shows activity or estimating the strength of the signal species, and displaying classification results based on combination of activities of the plural Hb signal species in a single chart. A living body light measuring device using the brain activity analyzing method and displaying method of the invention makes it possible to detect sites where brain activity is generated with a high precision.