Fragrance influences the psychophysiological state of a person; the volume of fingertip plethysmography is consequently affected by the aspiration of aroma. In this study, stimulation threshold at the time of aroma suction and emotional change around the discrimination threshold were evaluated by analyzing both a questionnaire and fingertip plethysmograph measurement. We built a fragrance generator to confirm the stimulus threshold, discrimination threshold, and acclimatization time of smell. Participants were asked to take a subjective evaluation of aroma intensity, comfortableness (comfort/discomfort), and aroma frequency in real time. The results confirmed the chaotic nature of the time series data of the fingertip plethysmographs. Moreover, the fingertip plethysmographs fluctuated when the participants responded that it did not smell in the subjective evaluation and when the maximum Lyapunov exponent increased, as the aroma fluctuation of the fingertip plethysmographs enlarged, corresponding to the uncomfortable values of the subjective evaluation.