An ink jet pigment ink containing water, a pigment, a water-soluble organic solvent and a graft copolymer, wherein the graft copolymer has a hydrophilic segment and a hydrophobic segment, the hydrophobic segment is being obtained by copolymerizing an anionic monomer and an aromatic monomer represented by the following formula (1), and the hydrophilic segment is being obtained by polymerizing an anionic monomer wherein Ar is an aromatic ring selected from a benzene ring, a condensed benzene ring and a hetero-aromatic ring, or a derivative thereof, R is H or CH3, and X is O or NH.