The present invention relates to an azo compound represented by the following formula (1) [wherein, A represents a naphthyl group having a substituent, R1 to R6 each independently represent a hydrogen atom, an alkyl group having a carbon atom number of 1 to 5, an alkoxy group having a carbon atom number of 1 to 5, a sulfo group, or an alkoxy group having a sulfo group and a carbon atom number of 1 to 5, and X represents a benzoylamino group having a substituent, a phenylamino group having a substituent, a phenylazo group having a substituent, or a naphthotriazole group having a substituent] and a salt thereof. By using the azo compound or a salt thereof of the present invention, a neutral color polarizing plate and a color polarizing plate for a liquid crystal projector being excellent in polarization performance and durability.