An illumination device for a refrigerator and a method of controlling the same are provided. The illumination device includes a lamp assembly that irradiates light to an inside of a storage chamber of the refrigerator, a base plate mounted on a side within the storage chamber, wherein the lamp assembly is provided on a side of the base plate, a watertight cover formed to enclose the lamp assembly blocking direct penetration of water into the lamp assembly, and at least one fastening device formed on a side of the base plate. The at least one fastening device surrounds an outer surface and an inner surface of entire lower edge of the watertight cover along a side of the watertight cover forming a recess-prominence engagement with the watertight cover. Lamps provided in the lamp assembly are individually controlled through a manipulation panel mounted on the main body.