PROBLEM TO BE SOLVED: To provide an aqueous ink composition for a writing instrument, without forming feathering in handwriting by containing a polyglutamic acid in the ink composition, also showing a good ink ejecting property so as not to form blur, and suitable for a marking pen equipped with a pen body consisting of a fiber bundle resin-processed material or the pen body consisting of a plastic molded material. SOLUTION: This aqueous ink composition for the marking pen containing at least water, water-soluble organic solvent and the polyglutamic acid is provided by suitably containing 0.01 to 1 wt.% polyglutamic acid in the total amount of the ink composition. COPYRIGHT: (C)2008,JPO&INPIT
