A method for determining whether a test bacterium is a class C beta-lactamase-producing bacterium. Spots of a class C beta-lactamase inhibitor and a beta-lactam drug are applied at an interval on the surface of a solid medium that has been coated with the test bacterium, the solid medium is cultured, and following culturing, determining whether or not the inhibitory zone formed around the beta-lactam drug has extended toward the class C beta-lactamase inhibitor. A mixture of class C beta-lactamase inhibitor and beta-lactam drug and a beta-lactam drug in spots are applied at an interval on the surface of a solid medium that has been coated with the test bacterium, the solid medium is cultured, and following culturing, observing the difference between the inhibitory zone formed around the mixture and the inhibitory zone formed around the beta-lactam drug. A kit for determining class C beta-lactamase-producing bacteria, in which a disk containing a class C beta-lactamase inhibitor and a disk containing a beta-lactam drug are arranged on a striplike base. A kit for determining class C beta-lactamase-producing bacteria, in which a disk containing both a class C beta-lactamase inhibitor and a beta-lactam drug and a disk containing a beta-lactam drug are arranged on a striplike base. Provided are a method for readily detecting class C beta-lactamas-producing bacterium and kits performing the method.