In a method of shielding a circuit device, a circuit board on which an electronic component has mounted and which has a ground connection portion is provided. An entire portion of the circuit board is inserted into a shield pack having a sack shape. The shield pack has an insulating layer as an innermost layer and an electric conductive layer as an outermost layer. The insulating layer of the shield pack is contacted with the electronic component and the circuit board. The ground connection portion of the circuit board is connected to the electric conducive layer of the shield pack.