A closing member for an opening formed on a panel configuring an outer surface of an airframe of an aircraft, the closing member comprising: the panel having a facing surface; a closing member body configured to be placed on one surface side of the panel and to have an external dimension larger than an external dimension of the opening to close the opening; a ring-shaped clamp member configured to be placed on another surface side of the panel and to have an external dimension larger than the external dimension of the opening; and a fastener for fastening the closing member body and the clamp member together, with the panel then being interposed between an outer peripheral part of the closing member body and an outer peripheral part of the clamp member, and the closing member comprising a first spacer and a second spacer configured to lie between the outer peripheral part of the closing member body and the facing surface of the panel facing the outer peripheral part around the opening, the first spacer being interposed between the outer peripheral part of the closing member body and the facing surface, when the opening is closed with the closing member body, the second spacer being interposed between the outer peripheral part of the closing member body and the facing surface at least in a state when the first spacer has fallen off, characterized in that the second spacer is formed of a material softer than a material of the first spacer, and is interposed between the outer peripheral part of the closing member body and the facing surface of the panel, when the first spacer is interposed between the outer peripheral part of the closing member body and the facing surface of the panel. the panel having a facing surface; a closing member body configured to be placed on one surface side of the panel and to have an external dimension larger than an external dimension of the opening to close the opening; a ring-shaped clamp member configured to be placed on another surface side of the panel and to have an external dimension larger than the external dimension of the opening; and a fastener for fastening the closing member body and the clamp member together, with the panel then being interposed between an outer peripheral part of the closing member body and an outer peripheral part of the clamp member, the closing member comprising a first spacer and a second spacer configured to lie between the outer peripheral part of the closing member body and the facing surface of the panel facing the outer peripheral part around the opening, the first spacer being interposed between the outer peripheral part of the closing member body and the facing surface, when the opening is closed with the closing member body, the second spacer being interposed between the outer peripheral part of the closing member body and the facing surface at least in a state when the first spacer has fallen off, characterized in that the second spacer is formed of a material softer than a material of the first spacer, and is interposed between the outer peripheral part of the closing member body and the facing surface of the panel, when the first spacer is interposed between the outer peripheral part of the closing member body and the facing surface of the panel.