A first transparent sealing member is used in a package accommodating at least one optical element, and is attached to a mounting substrate having a mounting surface for the optical element. In the first transparent sealing member, at least one corner part among a plurality of corner parts configured by a surface facing the mounting substrate and a surface along the mounting surface of the mounting substrate has a curved shape, and punctiform minute recessed parts are formed on the surface of the curved shape. The average presence frequency of the minute recessed parts is 100,000 to 3,000,000 inclusive per 1 mm2.