A method is described for making determinations on or classifying the pain of an estimation subject on the basis of the brainwaves of the estimation subject. This method includes: (a) stimulating the estimation subject at a plurality of levels of stimulation intensity; (b) acquiring brainwave data for the estimation subject; (c) extracting a brainwave feature quantity from the brainwave data or the analysis data; (d) for plugging the feature quantity into a Sparse model analysis, making the feature quantity approach a quantitative level and/or a qualitative level for pain, and estimating or making a determination on a pain level. Another method is described including comparing of brainwave data or analysis data from the 2,000 msec following the earliest of an induced brainwave component, an initial-event-related voltage component, and 250 msec after a target stimulus has been applied.