To synthesize a speech which would not incorrectly be heard by extracting a characteristic expression from a text and changing a way of pronouncing the characteristic expression part.

(S1) Reading printed in KANA (Japanese syllabary) of KANJI (Chinese character) is given to a text 1 of KANA-KANJI mixed sentences by using a reading dictionary and an accent dictionary 2 and an accent type is set. (S2) The proper expression (e.g. a telephone number) is extracted by using morpheme information and reading information outputted through text analysis. (S3) Rhythm parameters (fundamental frequency pattern of a speech, continuance of a phoneme, power of the speech, etc.) are generated. (S4) General speech (continuously generated speech) synthesis unit 6 are used for selection in speech synthesis of an ordinary text and the proper expression (a part sandwiched between a label and a tag) is selected by using speech synthesis units of monosyllabic pronunciation (independent pronunciation of a monosyllable). (S5) Signal processing of a selected speech synthesis unit is performed to match rhythm parameters, thereby outputting a synthesized speech.