A reliable optical semiconductor device can include an optical semiconductor chip sealed in a surrounding soft resin and in a hard resin that is harder than the soft resin. The hard resin can include an aperture that is configured to relieve a state of hermetic sealing for the soft resin (allows the soft resin to expand during volume change due to temperature fluctuations, etc.) and can be formed in a direction that imposes substantially no optical influence on a function of the optical semiconductor chip. The soft resin and the hard resin can be employed for double sealing to form the highly reliable optical semiconductor device without requiring additional space. This is effective to solve a problem caused in a conventional optical semiconductor device associated with double sealing by soft and hard resins, which requires a space between both resins and results in deteriorated performance, for example, a reduced amount of light.