A microbicidal agent comprising as an effective ingredient at least one selected from the group consisting of p-hydroxybenzaldehyde, 5,7,4-trihydroxy-3,5-dimethoxyflavone, 3-hydroxypyridine and vanillin, and a microbicidal composition comprising the microbicidal agent.本發明之目的在提供抗微生物劑及含有該抗微生物劑之抗微生物性組成物。更詳言之,本發明係含有選自對-羥基苯甲醛、5,7,4’-三羥基-3’,5’-二甲氧基黃酮、3-羥基吡啶及香草素所構成組群之至少一種作為有效成分之抗微生物劑及含有該抗微生物劑之抗微生物性組成物。