The present invention provides a water-based ink for ink-jet printing which is excellent in ejection stability and storage stability, in particular, excellent in quick-drying fixing properties and image uniformity when printing characters or images on a low-water absorbing recording medium, and an image forming method using the water-based ink. The present invention relates to [1] a water-based ink for ink-jet printing, including a pigment, a water-insoluble polymer, an organic solvent (C) and water, in which the organic solvent (C) includes diethylene glycol isopropyl ether (DEGPE) and an organic solvent (c2) having a 1-octanol/water partition coefficient that is smaller than that of DEGPE; a total content of the pigment, the water-insoluble polymer and DEGPE in the water-based ink is not less than 5.0% by mass; and a value obtained by multiplying a total content of the pigment and the water-insoluble polymer in the water-based ink by a content of DEGPE in the water-based ink is from 10 and 300; and [2] an image forming method including the steps of mounting a container filled with the water-based ink to an ink-jet printing apparatus equipped with an ink ejecting means; and ejecting the ink onto a recording medium having a water absorption of from 0 to 10 g/m2 as measured by contacting with pure water for 100 ms to print characters or images thereon.