To obtain a highly safe magenta color water-base ink composition used in color printing including ink jet printing, having hue and clearness suitable for obtaining various formulated colors and giving recorded matter having high light resistance, color fastness and color value by using a specified disazo compound as the colorant.

This composition contains a disazo compound which, in the form of a free acid, is represented by the formula (wherein R1 is H or carboxyl; one of R2 and R3 is H, and the other is sulfone; X is chlorine or hydroxyl; and Y is 2,5-dicarboxy-1,4-phenylene, 5-carboxy-1,3phenylene or 2-carboxy-1,4- phenylene when R1 is H; or is 1,4-phenylene, 1,3-phenylene or 2-carboxy-1,4- phenylene when R1 is carboxyl). This compound being a colorant is contained in an amount of about 0.1-20wt.% based on the composition.