Single molecular memory operation was observed on a porphyrin derivative by scanning tunneling microscopy at room temperature. A porphyrin derivative with four disulfide groups was chemically synthesized and chemisorbed on a Au(111) surface. Coulomb blockade behaviors and switching behaviors in current-voltage (I-V) characteristics were observed on a single porphyrin derivative by scanning tunneling spectroscopy. Based on the switching behaviors, the memory operation of
electrical conductance in the porphyrin derivative was demonstrated by applying a programmed pulse sequence with an on/off ratio of 2.9 at room temperature.