1. A text to speech synthesizer, comprising: a text analyzer for analyzing Japanese text data; a facial character reading assignment unit for assigning facial character readings to character string portions of text analysis results determined to correspond to facial characters; and a speech synthesizer for outputting synthesized speech based on the analysis results of the text analyzer, wherein the facial character reading assignment unit is constituted by; a facial character determining unit for determining whether or not a symbol is a symbol constituting a facial character using an outline symbol table, a characteristic extraction unit for extracting characteristic symbols used in facial characters from facial character strings determined to be for facial characters and assigning facial characters corresponding to characteristic symbols, and a reading selection unit for outputting readings allotted to extracted reading numbers, with readings being allotted to the facial character strings according to the number of appearances of characteristic symbols in the facial characters.