1. Speech information processing apparatus, comprising: representative pattern memory means for storing a plurality of representative pitch patterns from natural speech data and attribute data corresponding to representative pitch patterns, the representative pitch pattern as being arranged by prosody units; clustering means for classifying a plurality of prosody units to a cluster according to attribute data of each of the the prosody units; extraction means for extracting a generated pitch pattern corresponding to the prosody units classified to the cluster; transformation parameter generation means for generating a transformation parameter by evaluating an error between the generated pitch pattern and a transformed representative pattern; and representative pattern generation means for generating an updated representative pattern by calculating an evaluation function of the generated pitch pattern and the transformation parameter.