The first invention relates to a water-based ink for ink-jet printing which includes colorant-containing polymer particles (A) obtained by dispersing a colorant with a water-soluble polymer (x) and a water-insoluble polymer (y), a water-soluble organic solvent (B) and water, wherein a weight ratio of the water-insoluble polymer (y) to the water-soluble polymer (x) [(y)/(x)] is from 2.0 to 5.0, and a content of the water-soluble organic solvent (B) in the ink is from 10 to 70% by weight. The water-based ink for ink-jet printing according to the first invention is excellent in ejection property and optical density and exhibits a low viscosity. The second invention relates to a process for producing a water dispersion for ink-jet printing, which includes a step (I) of mixing a dispersion of a colorant with an emulsion of a water-insoluble polymer containing an organic solvent; a step (II) of subjecting the resulting mixture to dispersing treatment to obtain a dispersion of the colorant onto which the water-insoluble polymer is deposited; and a step (III) of removing the organic solvent from the resulting dispersion. The water dispersion produced by the process of the second invention is capable of exhibiting a high optical density suitable for high-speed printing.