An electronic device comprising: a first ground conductor layer positioned at an underside of a first insulation layer; a second ground conductor layer positioned at an upper side of the first insulation layer; a second insulation layer positioned at an upper side of the second ground conductor layer; a first connection pattern (34, 34a) formed in an inside wall of a first opening penetrating the first insulation layer and the second insulation layer, said first connection pattern (34, 34a) interconnecting the first ground conductor layer and the second ground conductor layer; a conductive member connected to the first ground conductor layer; an electronic element (37a, 37b) mounted on the conductive member and grounded to the conductive member; and a third insulation layer positioned at an underside of the first insulation layer, characterized in that: said third insulation layer comprises a second opening having an opening dimension that is larger than an opening dimension of the first opening; the conductive member is provided in the first opening and the second opening; a second part of the conductive member positioned in the second opening has a larger diameter than a first part of the conductive member positioned in the first opening; and an upper surface of the second part of the conductive member positioned in the second opening is connected to the underside of the first ground conductor layer. a first ground conductor layer positioned at an underside of a first insulation layer; a second ground conductor layer positioned at an upper side of the first insulation layer; a second insulation layer positioned at an upper side of the second ground conductor layer; a first connection pattern (34, 34a) formed in an inside wall of a first opening penetrating the first insulation layer and the second insulation layer, said first connection pattern (34, 34a) interconnecting the first ground conductor layer and the second ground conductor layer; a conductive member connected to the first ground conductor layer; an electronic element (37a, 37b) mounted on the conductive member and grounded to the conductive member; and a third insulation layer positioned at an underside of the first insulation layer, characterized in that: said third insulation layer comprises a second opening having an opening dimension that is larger than an opening dimension of the first opening; the conductive member is provided in the first opening and the second opening; a second part of the conductive member positioned in the second opening has a larger diameter than a first part of the conductive member positioned in the first opening; and an upper surface of the second part of the conductive member positioned in the second opening is connected to the underside of the first ground conductor layer. said third insulation layer comprises a second opening having an opening dimension that is larger than an opening dimension of the first opening; the conductive member is provided in the first opening and the second opening; a second part of the conductive member positioned in the second opening has a larger diameter than a first part of the conductive member positioned in the first opening; and an upper surface of the second part of the conductive member positioned in the second opening is connected to the underside of the first ground conductor layer.