According to an aspect of an embodiment, an apparatus for converting text data into sound signal, comprises: a phoneme determiner for determining phoneme data corresponding to a plurality of phonemes and pause data corresponding to a plurality of pauses to be inserted among a series of phonemes in the text data to be converted into sound signal; a phoneme length adjuster for modifying the phoneme data and the pause data by determining lengths of the phonemes, respectively in accordance with a speed of the sound signal and selectively reducing the length of at least one of the pause in the text data to a pause length which is less than the pause length corresponding to the speed of the sound signal; and an output unit for outputting sound signal on the basis of the adjusted phoneme data and pause data by the phoneme length adjuster.