Abstract: A hepatotoxin produced by cyanobacteria, microcystin (MC), was chromatographically discriminated with newly prepared artificial trapping devices. MC involves up to 70 kinds of homologues; and because homologues have similar toxicity, effective removal and analysis methods have been required. As a trapping device to discriminate MC, we have developed a novel technique for preparation of the "imprinted recognition site" into the crosslinked nano-scale structure, namely "Fragment Imprinting Effect." This technique is simple, and its possible application fields, are relatively broad. We have demonstrated the recognition for MC homologues through the combination of two different artificial molecular recognition devices prepared through fragment imprinting technique