An azo-compound, free acid form of which is represented by the following formula (I): wherein A and B represent, independently with each other, a phenyl having one or two groups selected from sulfo and carboxyl or a naphthyl having 1 to 3 sulfos; R1, R2, R3, R4, R5 and R6 represent, independently with each other, hydrogen, lower alkyl or lower alkoxy; and X represents —N═N— or —NHCO—, and a dye polarizing film containing the azo-compound in a polarizing film base, which exhibits a high polarizing performance and is excellent in durability and light fastness, are provided.