PURPOSE: To produce a large amount of an antithrombogenetic medical material at a low cost, by coating or impregnating a collagen-containing solution to a synthetic polymeric material and immobilizing protamine to the collagen with a crosslinking agent, thereby heparinizing the collagen.

CONSTITUTION: A collagen-containing solution is coated to or impregnated in a synthetic polymeric material (e.g. polyurethane, polyvinyl chloride, etc.), and protamine is immobilized to the collagen with a crosslinking agent (e.g. hexamethylene diisocyanate), thereby bonding heparin to protamine to effect the heparinization of collagen. The objective antithrombogenetic medical material containing heparinized collagen integrated to a synthetic polymeric material can be produced by this process. A large amount of the objective medical material having excellent antithrombogenetic property, cell affinity, physical strength and uniformity can be produced at a low cost by integrating heparinized collagen with a synthetic polymeric material.