A shell member that is ground-connected to a connected object is constituted by a first shell that faces the connected object and entirely covers a contact member and a second shell that faces the first shell in a part between a connecting object and the connected object. Each of the first and second shells is provided with ground contact points with a ground conducting path of the connecting object and a ground conducting path of the connected object, with a signal transmission path sandwiched between ground paths by the first and second shells and configured to achieve satisfactory electromagnetic shielding of the signal transmission path.