PURPOSE: To obtain a dispersant useful for coating compound, having excellent dispersibility and adhesivity, containing a specific modified polymer.

CONSTITUTION: The objective dispersant comprising a modified polymer prepared by reacting an unsaturated polymer such as polybutadiene with an organic compound [e.g. glyoxylic acid; amount of glyoxylic acid used is preferably 0.01-20 pts.wt. based on 100 pts.wt. polymer] or containing a carboxyl group and an aldehyde group in the presence of a protonic acid such as sulfuric acid or a Lewis acid such as BF3 or a polymer prepared by coupling an anion living polymer of 1,3-butadiene, etc., with a tin compound such as methyltrichlorotin or an isoprene-based polymer treated with tin tetrachloride. Fine granular particles having improved dispersibility to various mediums and the stable dispersion are obtained by treatment with the dispersant.