An object of the present invention is to provide a biosensor comprising a
hydrogel capable of immobilizing a physiologically active substance
thereon, which can be produced conveniently by use of a safe material,
and a method for producing the same. The present invention provides a
method for producing a biosensor, which comprises bringing a polymer
containing an activated carboxyl group into contact with a substrate
surface coated with an organic layer having an amino group to thereby
bind the polymer to the organic layer.