An optical semiconductor element 2 is mounted on a lead frame 1, the optical semiconductor element 2 is encapsulated with a mold resin portion 14 of a first layer that has light permeability, and the mold resin portion 14 of the first layer is encapsulated with a mold resin portion 15 of a second layer that has light permeability. Then, a coefficient of linear expansion of the mold resin portion 14 of the first layer is made smaller than a coefficient of linear expansion of the mold resin portion 15 of the second layer.