A heat dissipating fan is housed in the opening of a chassis in the direction of thickness of the fan; a plurality of holding portions provided on the edges of the opening support the heat dissipating fan, parallel to the surface of the chassis; a plurality of elastic members provided on the two adjoining edges of the opening, respectively, urge the heat dissipating fan in the respective directions of the opposed edges of the opening to position the fan; and further a holder is provided with a plurality of elastic portions around ventilating openings corresponding to a blower window of the heat dissipating fan, and the elastic portions are abutted against the top surface of the peripheral portion of an outer casing of the heat dissipating fan to urge the heat dissipating fan perpendicularly to the face of the chassis.