1. A speech synthesizing method comprising: the extraction step of extracting a plurality of small speech segments from a speech waveform; the prosody control step of processing the plurality of small speech segments to control prosody of the speech waveform while limiting processing for a selected small speech segment of the plurality of small speech segments; and the synthesizing step of obtaining synthesized speech by using the speech waveform for which prosody control is performed in the prosody control step.