To provide an inkjet black ink having excellent image durability and ink discharge properties and an ink set, the inkjet black ink, which contains a dye having a .lamda.max of from 500 nm to 700 nm and a half-band width of 100 nm or more in an absorption spectrum of a diluted solution standardized at an absorbance of 1.0 at the .lamda.max, has the change ratio of absorbance at the .lamda.max in the visible region, specified in the specification; and the inkjet ink set containing at least two black inks having different densities has the relationship among the at least two black inks, specified in the specification.