The speed of an input speech is changed without any change of the pitch of the input speech. Raw data of a speech are stored so that the speed of the speech can be modulated continuously on the basis of the raw data of the speech. In the speech speed conversion method, a speech speed conversion process for the input speech is carried out in a period designated when speech speed conversion is needed, which the speech speed conversion is not carried out in the other period. Further, in the speech speed conversion apparatus having a unit for inputting a speech, a speech speed conversion unit for changing the speed of the input speech, and a unit for supplying the output of the speech speed conversion unit as an output speech to listener's ears, the apparatus further includes a speech speed conversion switch, and a unit for outputting a speech while changing the speech speed of the input speech in a period in which the speech speed conversion switch is turned on, but for outputting a speech without any change of the input speech in the other period in which the speech speed conversion switch is turned off.