Provided is a pigment dispersant for improving the dispersibility of an azo pigment for a water-insoluble solvent. More specifically, provided is a polyester, including at least one unit represented by one of the following formula (1) and the following formula (2): in the formula (1) and the formula (2): R1 represents an alkyl group having 1 to 6 carbon atoms or a phenyl group; R2 to R6 each represent a hydrogen atom, a COOR7 group, or a CONR8R9 group, provided that at least one of the R2 to R6 represents the COOR7 group or the CONR8R9 group; and the R7 to R9 each represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.