This invention relates to a foamed resin sheet containing closed-cells which have a specific average diameter and a specific volume ratio. The foamed resin sheet of this invention is excellent in light reflectance or light transmittance to visible light and is also excellent in light diffusing capability, and in particular it is suitable as a light reflective plate or light diffusing plate to be incorporated and used in a direct backlight unit for a large-screen liquid crystal display or a 15- to 39-inch large-screen liquid crystal television set. The industrial effect that this invention produces is remarkable.