The present invention relates to a process for producing an optical semiconductor device, the process including: disposing a sheet for optical-semiconductor-element encapsulation including a resin sheet A and a plurality of resin layers B discontinuously embedded in the resin sheet A and a plurality of optical semiconductor elements mounted on a substrate in such a way that each of the plurality of optical semiconductor elements faces either one of the plurality of resin layers B; and followed by embedding each of the plurality of optical semiconductor elements in either one of the plurality of resin layers B. According to the process of the invention, optical semiconductor elements can be embedded at once. As a result, an optical semiconductor device which is excellent in LED element protection and durability can be easily obtained. Consequently, the optical semiconductor device obtained can have a prolonged life.