We studied proteolysis of caseins in a Gouda/ Cheddar composite cheese manufactured by two different hard cheese methods during ripening. Protease activities by various enzymes in curd were observed in the wide range of pH 4.0 to 7.0, and those activities increased with the elapse of time of ripening. Composite cheese was mainly characterized by decomposition of α_s1-casein, which is one of the remarkable feature of cheese ripened by lactic acid bacteria. The existence of plural exopeptidases was suggested.