The present invention relates to a method for producing dextran polymer-based amplified nucleic acid aptamer nanoconstructs which efficiently and selectively capture a specific target molecule, the method comprising linking a short nucleic acid sequence or a complementary sequence for formation of nanoconstructs and a nucleic acid aptamer sequence for capture of the specific target molecule to a dextran polymer by a chemical reaction, mixing the resulting polymer/nucleic acid substances with each other to form nanostructures, subjecting the nanostructures to rolling circle amplification, thereby forming a nucleic acid aptamer having a repeated structure. The dextran polymer-based amplified nucleic acid aptamer nanoconstructs have the effect of efficiently and selectively capturing a specific target molecule.