The invention relates to an alkoxylated polyethyleneimine hydrophilically-modified fiber, wherein the alkoxylated polyethyleneimine has a weight average molecular weight of 600 to 25,000 and contains 1 to 40 alkylene oxide units per nitrogen atom. The invention also relates to a method of improving hydrophilicity of fiber comprising impregnating the fiber with an aqueous solution containing an alkoxylated polyethyleneimine, wherein the alkoxylated polyethyleneimine has a weight average molecular weight of 600 to 25,000 and contains 1 to 40 alkylene oxide units per nitrogen atom. The invention also relates to use of the alkoxylated polyethyleneimine in improving hydrophilicity of fiber.