1. An apparatus for voice synthesis comprising: a word database for storing data of a plurality of words and a plurality of voices corresponding to the words, respectively; a syllable database for storing data of a plurality of syllables and a plurality of voices corresponding to the syllables, respectively; a processor for executing a process including: extracting a word from a document, determining whether data of a word corresponding to the extracted word is included in the word database, extracting data of a voice associated with the word corresponding to the extracted word from the word database when the extracted word is included in the word database, and generating a voice signal based on the extracted voice data associated with the word corresponding to the extracted word, and extracting data of a voice associated with one or more syllables corresponding to the extracted word from the syllable database when the extracted word is not found in the word database, and synthesizing a voice signal based on the extracted voice data associated with the one or more syllables corresponding to the extracted word; a speaker for producing a voice based on either of the generated voice signal and the synthesized voice signal; and a display for selectively displaying the extracted word when the voice based on the synthesized voice signal is produced by the speaker.