To obtain an aqueous pigment dispersion not liable to coagulate, not clogging in writing tools, printers, etc., not creating blank spaces in written or printed records, excellent in dispersion stability and color development and useful for cosmetics, etc., by wet-grinding a pigment in an aqueous medium, while treating the pigment with ozone, etc.

This method for producing an aqueous pigment dispersion comprises wet-grinding a pigment such as an organic pigment, e.g. pigment yellow, in an aqueous medium, while treating the pigment with ozone (the concentration is preferably 0.5-15wt.%) or hydrogen peroxide (the concentration is preferably 5-10wt.%). The pigment in the aqueous pigment dispersion has an average particle diameter of ≤0.5μm.