Active oxygen species, which are excessively generated in the body, cause diseases such as cancer and inflammation. Since the measurement of the concentration of active oxygen species in vivo is important from the viewpoint of diagnosis of various diseases and evaluation of pharmacological action of therapeutic agents, establishment of a rapid quantitative measurement method in vivo is eagerly desired. Previously, we have reported the construction of active oxygen sensor using thiophene tetrasubstituted iron porphyrin. It has been suggested that thiophene tetrasubstituted porphyrins polymerize randomly to build a three-dimensional structure, on the other hand, conductive polymers show high conductivity in a linear structure. As the results of the detectability and quantitative evaluation of active oxygen species, it was revealed that the thiophene monosubstituted porphyrin sensor showed higher current responsiveness than the thiophene tetrasubstituted porphyrin.