A hands-free telephone conversation apparatus can reduce negative influence of an echo on a sound to be transmitted to a far-end user without deteriorating the sound. When a MPU determines that a mobile phone receives an incoming call, and a user starts to talk on the mobile phone, in accordance with an operation of an input device connected to an in-vehicle bus line, a MPU controls the mobile phone to have the mobile phone output, to the DSP, a sound signal indicative of a sound to be transmitted to the far-end user, and to have a switch select a loudspeaker, installed in an vehicle without being directed to the microphone, as a loudspeaker for outputting a sound received from the far-end user.