The invention provides an emotional state determination method capable of quantitatively and accurately measuring an emotional state of a human being without requiring a special measuring environment. At least one of oxy-hemoglobin densities and deoxy-hemoglobin densities in blood of a plurality of measurement regions of a human brain cortex of a subject 1 are measured in time series, respectively, using a near-infrared spectroscopy. Then, cross-correlation coefficients of plural sets of time-variable change data are computed for each time (for each sampling period). Each of the plural sets of the time-variable change data comprises two of the time-variable change data which are selected by permutations and combinations from among at least one of the time-variable change data on the measured oxy-hemoglobin densities and the time-variable change data on the measured deoxy-hemoglobin densities. Then, by analyzing time-variable change patterns of the computed cross-correlation coefficients of the plural sets of the time-variable change data using a predetermined determination method, the emotional state of the subject is quantitatively measured.
