Abstract: Disclosed is an ultra-slim telephone set in which a plurality of circuit elements of telephone are mounted on both sides of the PCB in a multi-layer manner so as to reduce the telephone body and the handset is made earphone-typed to be hung in one of ears and can be separated/attached from/to the body with the use of the phone jack so as to make the size of the top side of the telephone be as small as a keypad, so that the telephone set can be hand-held and mobile making the user who especially may have to work with both hands have an improved work environment.