Disclosed is an azo compound represented by the formula (1) or (2) or a salt thereof. The azo compound or the salt thereof has an excellent light-polarizing property, and is extremely useful as a dichroic dye for use in a polarizing plate that shows less color leakage in a visible light range or a polarizing plate for a liquid crystal projector comprising the aforementioned polarizing plate. (1) (2) wherein R1 represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a hydroxyl group, a sulfonate group or a carboxyl group; R2 to R5 independently represent a hydrogen atom, a loweralkyl group, a lower alkoxy group or an acetylamino group; X represents a benzoylamino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, or a naphthotriazole group which may have a substituent; m represents a numeral number of 1 or 2; and n represents a numeral number of 0 or 1.