Provided is a drug effective for the prevention or treatment of diabetic nephropathy. The preventative or therapeutic agent for diabetic nephropathy contains, as an active ingredient, a hydroquinone derivative represented by general formula (1) (wherein, R1 represents a C4-8 alkyl group, and R2 represents a hydrogen atom, a C2-6 alkyl carbonyl group or a C2-6 alkoxy carbonyl group).