Disclosed is a complex which comprises a carbon nanotube and a modified polysaccharide having a backbone chain with the side thereof being introduced with monosaccharide or oligosaccharide residues. The polysaccharide is preferably β-1,3-glucan. The complex is prepared by admixing a solution of the modified polysaccharide dissolved in an aprotic polar solvent or a strong alkali solution with an aqueous dispersion of the carbon nanotube, and incubating the mixture.