A hands-free device includes a cellular phone of a driver, driver's speakers that output sounds to the driver, front speakers and rear speakers that output sounds widely in a car, a detection unit that outputs a detection signal to indicate whether there is a fellow passenger in the car or not, and control equipment that communicates with the cellular phone. In the case that the control equipment receives a telephone communication voice signal indicating telephone conversation voice of another party of the telephone conversation from the cellular phone, based on the detection signal outputted from the detection unit, when the control equipment judges that there is no fellow passenger, the control equipment has the telephone conversation voice outputted mainly from the front speakers and the rear speakers, and when the control equipment judges that there is a fellow passenger, the control equipment has the telephone conversation voice outputted mainly from the driver's speakers.