Abstract: When a delivered speed of a listening speech (speech speed) is slowed down, a connection order generator (8) always monitors a data length of input speech, an output data length calculated previously by a conversion function concerning a preset scaling factor, and a data length of actual output speech in predetermined processing unit, then decides connection order not to cause inconsistency among them. The speech data and the connection data are connected without omission of speech information by controlling a speech data connector (9). When power of an input signal data is calculated to discriminate a speech interval and a non-speech interval, a threshold value for power is decided according to a maximum value of the power and difference between the maximum value and a minimum value.