The amyloidosis of amyloid β (1-42) was investigated by the well-defined glyco-cluster interface. We prepared monovalent, divalent, and trivalent 6-sulfo-N-acetyl-D-glucosamine immobilized substrates. The interaction between amyloid β and 6-sulfo-N-acetyl-D-glucosamine was amplified by multivalentcy of divalent and trivalent 6-sulfo-N-acetyl-D-glucosamine. The morphology of amyloid β were investigated by AFM, and we found the morphology of amyloid β aggregates were determined by the kinds of displayed saccharide-valency. Amyloid β had tendency to form spherical objects on the multivalent 6-sulfo-N-acetyl-D-glucosamine, but form fibrils on the monovalent 6-sulfo-N-acetyl-D-glucosamine. Spherical amyloid β was more toxic than fibrillar amyloid β to HeLa cells. These results suggested that the multivalency of was significant in its morphology and aggregation effects at the surface of the cell membrane mimic.