The present invention provides an ink composition containing a pigment dispersed uniformly in a solvent and a block polymer having an ionic functional group, an image-forming method and an image-forming apparatus employing the ink composition.The composition comprises a pigment, a solvent and a polymer having an ionic functional group, an acid residue, or a base residue at the terminal. The polymer having an ionic functional group, an acid residue, or a base residue at the terminal is a block polymer of ABX type having A, B, and X segments, wherein A and B are respectively a block segment having a vinyl ether structure as the repeating unit, and X is a terminal segment having an ionic functional group, an acid residue, or an base residue.