PURPOSE: To obtain the titled compound useful as a comonomer by a simple reaction operation in high yield inexpensively, by heating a corresponding triazine as a raw material under reduced pressure in the presence of a polymerization inhibitor.

CONSTITUTION: A corresponding triazine {adduct of 2-[β-(2'-methylimidazol-1')]- ethyl-4,6-diamino-S-triazine with isocyanuric acid} shown by the formula I easily obtainable from acrylonitrile, 2-methylimidazole, dicyandiamide and isocyanuric acid is heated in the presence of a polymerization inhibitor such as Na2S, etc. in a reaction solvent retainable under reduced pressure at 5W20mmHg at 180W 320°C for ≤1hr to give the desired compound shown by the formula II (T.V. for short), attached 2-methylimidazole shown by the formula III and isocyanuric acid shown by the formula IV. Then, the compounds are washed with an alkali aqueous solution to remove the compounds shown by the formulas III and formula IV, and the residue is recrystallized with water, to give V.T. shown by the formula II.