A vent grid has parallel first electrically-conductive members and parallel second electrically-conductive members intersecting with the first electrically-conductive members. The intersection between the first and second electrically-conductive members is forced to have a larger cross-sectional area. The characteristic impedance thus increases. The electric current flowing through the first and second electrically-conductive members turns over at the boundary between the intersection and the first and second electrically-conductive members. The flow of the electric current is in this manner interrupted. Accordingly, the vent grid fails to induce electromagnetic wave. Moreover, the electrically-conductive piece is merely located at a corner of the opening. Decrease in the percentage of the opening is thus suppressed to the utmost per a unit area. A sufficient airflow can be established through the vent grid. Decrease in the cooling efficiency and performance can be suppressed.