A plurality of tasks of a speech synthesizing process in which at least one of speakers, emotion or situation at the time when speeches are made, and contents of the speeches is different are set (s1), word dictionaries, prosody dictionaries, and waveform dictionaries corresponding to respective tasks are organized (s2), and when a character string is to be synthesized is input with the task specified through a game system, etc., a speech synthesizing process is performed using the word dictionary, the prosody dictionary, and the waveform dictionary corresponding to the specified task (s3). Therefore, a speech message can be generated depending on the personality of a speaker, the emotion or situation at the time when a speech is made, and the contents of the speech.