An oscillator attachment structure which prevents inference by a beat signal caused by mixture of a reference oscillation signal from a PLL circuit and an oscillation signal from an oscillator. A plate conductive rubber member (16), electrically connected to a ground conductor (12), is provided on the lower surface of a circuit board, and the conductive rubber member is placed on a ground conductive member of a printed circuit board. The ground conductor and the ground conductive member are electrically connected to each other, and the circuit board can be sufficiently grounded to the PLL circuit on the printed circuit board.