1. An emotion detecting method for detecting an emotion of a subject, comprising the steps of: inputting a voice signal; detecting an intensity of a voice, a tempo expressing speed the voice emerges at, and intonation expressing an intensity-change pattern in each word the voice makes, based on the inputted voice signal; obtaining amounts of change in the intensity of the detected voice, tempo of the voice, and intonation in the voice, respectively; and generating signals expressing states of emotion of at least anger, sadness, and pleasure, respectively, based on the obtained amounts of change.