1. An emotion detecting method that performs an emotion detecting processing based on an audio feature of input audio signal data, comprising: an audio feature extracting step of extracting, as an audio feature vector, one or more of a fundamental frequency, a sequence of a temporal variation characteristic of the fundamental frequency, a power, a sequence of a temporal variation characteristic of the power, and a temporal variation characteristic of a speech rate from the audio signal data for each analysis frame, and storing the audio feature vector in a storage part; an audio feature appearance probability calculating step of reading the audio feature vector for each analysis frame and calculating the audio feature appearance probability that the audio feature vector appears on condition of sequences of predetermined emotional states corresponding to one or more types of emotions using a first statistical model constructed based on previously input learning audio signal data; an emotional state transition probability calculating step of calculating the probability of temporal transition of sequences of the predetermined emotional states as the emotional state transition probability using a second statistical model; an emotional state probability calculating step of calculating the emotional state probability based on the audio feature appearance probability and the emotional state transition probability; and an information outputting step of outputting information about the emotional state for each section including one or more analysis frames based on the calculated emotional state probability.