The present invention herein provides a gel for electrophoresis which comprises a gel prepared from single-stranded glucan which has β-1,3-glucoside bonds as a main chain and β-1,6-glucoside bonds on side chains, or a mixture of the glucan with a second polysaccharide, or acrylamide and/or derivative thereof; and a method for the preparation of a gel for electrophoresis comprising the steps of dissolving a glucan, which has β-1,3-glucoside bonds as a main chain and β-1,6-glucoside bonds on side chains, in a first solvent which can dissociate the helical structure of the glucan to thus form single-stranded glucan; removing the first solvent; dissolving the single-stranded glucan in a second solvent capable of dissolving the same; and then heat-treating the resulting solution. The pore size of the gel according to the present invention can easily be controlled, the gel permits the isolation and/or analysis of a nucleic acid or a protein whose molecular weight falls within a wider range and the gel never interferes with the detection, through the staining technique, of such a nucleic acid or a protein separated and developed on or within the gel.