To easily ground even with no space for adopting a screwing structure by forming a ground piece grounding a shell for an external interface connector facing its connecting port from the opening of a shield plate to the outside in an opening circumferential part of the shield plate.

An opening 7 for inserting an external interface connector 5 is formed in a front plate 3a of a shield plate. A ground piece 9 for grounding the connector is integrally formed in the upper side (an opening circumferential edge) of an opening 7 in such a state as gradually expanded in the inside of the front plate 3a toward the depth 5. When the external connector is connected to a connecting port 5b of the connector 5, for example, the grounding piece 9 relieves static electricity from the outside entering through the external connector, onto the shield plate. Preferably, a structure grounding to the shell 5a of the connector 5 with elasticity by the pressure contact force is adopted for the grounding piece 9.