The present invention provides a resinous hollow package that includes a moisture-proof island that is a planar structure disposed below a semiconductor element mounting surface of the resinous hollow package, the semiconductor element mounting surface having an area of 200 mm2 or more and the maximum wave height of a wave curve of 35 μm or less. The resinous hollow package of the invention has an excellent moisture resistance due to the moisture-proof island included therein. Further, since the flatness of the semiconductor element mounting surface is excellent, decrease in the amount of light in a peripheral portion of an image can be suppressed in a digital single-lens reflex camera or the like with a large solid-state image sensor, even when a wide angle lens is used. According to the method of producing the resinous hollow package of the invention, by carrying out insert-molding while fixing the moisture-proof island with projection(s) disposed to the mold to prevent displacement thereof, the resinous hollow package having the maximum wave height of the semiconductor element mounting surface of 35 μm or less can be provided.