3. The method according to claim 2 , before the outputting the converted speech in the voice characteristics of the sender, further comprising: conducting a search to determine whether the sender's first voice data is present in the voice database; extracting, from the voice database, voice data of the sender corresponding to the first text data based on a search result of the conducting the search; and transmitting the voice data of the sender extracted, wherein the extracting voice data comprises: extracting, from the voice database, voice data of the sender that matches a sentence included in the first text data; extracting, from the voice database, voice data of the sender that matches a word included in the first text data; and extracting, from the voice database, voice data of the sender that matches a syllable included in the first text data.
2. The method according to claim 1 , wherein the voice database comprises storing voice data of the sender of the first text data and text data corresponding to the second voice data for each sentence, each word, and each syllable.