The present invention relates to an optical-semiconductor device, which is prepared by: arranging a sheet for optical-semiconductor element encapsulation including an encapsulating resin layer capable of embedding an optical-semiconductor element and a wavelength conversion layer containing light wavelength-converting particles and being laminated directly or indirectly on the encapsulating resin layer, on an optical-semiconductor element-mounting substrate so that the encapsulating resin layer faces the optical-semiconductor element-mounting substrate; followed by compression-molding, in which the wavelength conversion layer is present on an upper part of a molded body in which the optical-semiconductor element is embedded therein, but is not present on a side surface of the molded body.