An object of the present invention is to provide antimicrobial agents that do not contribute to the emergence of drug-resistant microorganisms, that present less side effects, and that can be combined with other medications while causing less adverse effects. The present invention provides antimicrobial agents containing at least one member selected from the group consisting of: at least one hydrogen isotope selected from the group consisting of hydrogen atom (H)； 1H, 2H, 3H, 4H, 5H, 6H and 7H； hydrogen molecule (H2)； a metal hydride； hydrogen ion (H+)； hydride ion (H&minus；)； and atomic hydrogen. The antimicrobial agents of the present invention exhibit their antimicrobial action through the action of hydrogen, so they are less likely to induce emergence of drug-resistant microorganisms.
