According to one embodiment of the present application, a biosensor, the biosensor comprising: a reaction part including a magnetic nanoparticle complex, a first electrode, and a second electrode; and a sample introduction part forming a passage so that a sample can be introduced into the reaction part from an outside of the biosensor; wherein the magnetic nanoparticle complex includes a first capturing substance for capturing a first target substance, a magnetic nanoparticle, and a reaction substance that performs at least one of an oxidation reaction and a reduction reaction, wherein the magnetic nanoparticle complex has is magnetic in the reaction part, and has a property that mobility can be changed according to a change in a condition of the reaction part, wherein the first electrode, a second capturing substance for capturing a second target substance is fixed, wherein the second electrode is an electrode different from the first electrode, and characterized in that at least one of the first target substance and the second target substance is included in the sample, may be provided.