The present invention provides an anti-diacetylspermine specific monoclonal antibody which satisfies a specific measuring condition in an immunoreaction system between a solid-phased diacetylspermine and the anti-diacetylspermine specific monoclonal antibody, wherein the immunoreaction system comprises a sample diacetylspermine or sample N.sup.1-acetylspermidine to inhibit the immunoreaction; and the specific measuring condition is that the 50% inhibition activity against the immunoreaction by the diacetylspermine in the sample is at least 1,000 times as much as the 50% inhibition activity against the immunoreaction by the N.sup.1-acetylspermidine in the sample.