A method for detecting the presence and/or amount of Enterobacteriaceae bacteria in a sample selected from food or beverage samples, environmental samples, and biological samples, the method comprising the step of simultaneously detecting the presence and/or amount of Enterobacteriaceae bacteria of two or more different genera in the sample based on antigen-antibody reactions, wherein the step of detecting comprises: contacting the sample with an antibody that causes antigen-antibody reactions with components derived from the Enterobacteriaceae bacteria of two or more genera; and measuring the presence and/or intensity of the antigen-antibody reaction that occurs in the sample after contact, wherein the antibody is a monoclonal antibody having: as a heavy chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:1, and as a light chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:2; or as a heavy chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:3, and as a light chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:4; or as a heavy chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:5, and as a light chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:6. contacting the sample with an antibody that causes antigen-antibody reactions with components derived from the Enterobacteriaceae bacteria of two or more genera; and measuring the presence and/or intensity of the antigen-antibody reaction that occurs in the sample after contact, wherein the antibody is a monoclonal antibody having: as a heavy chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:1, and as a light chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:2; or as a heavy chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:3, and as a light chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:4; or as a heavy chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:5, and as a light chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:6. as a heavy chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:1, and as a light chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:2; or as a heavy chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:3, and as a light chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:4; or as a heavy chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:5, and as a light chain variable region sequence, the amino acid sequence having a homology of 80% or more to the amino acid sequence of SEQ ID NO:6.