The invention provides a sheet for optical-semiconductor element encapsulation, which has a multilayer structure including at least two resin layers. The at least two resin layers include: (A) an outermost resin layer (layer A) that is to be brought into contact with one or more optical semiconductor elements; and (B) a resin layer (layer B) disposed on the layer A and having a lower refractive index than that of the layer A. Also disclosed is a process for producing an optical semiconductor device using the sheet.