An apparatus for voice modulation in a mobile terminal comprises: a voice input unit being inputted a voice of a subscriber and generating an analog voice signal; a voice modulation unit for modulating the generated analog voice signal; an audio processor for converting the modulated analog voice signal into a digital signal; and an mobile station modem (MSM) for processing the digital signal to be suitable for a wireless transmission. Therefore, the apparatus for voice modulation in a mobile terminal is able to protect the privacy of subscriber by modulating the voice of subscriber during speaking on the phone, and is able to prevent the telephone harassment. Also, the voice of subscriber can be modulated variously as voice in a cave, child voice, devil voice, man's voice, woman's voice, and user defined effect sound, etc., and therefore, the various desires of mobile terminal user can be satisfied.