Electronegativity is one of the fundamental concepts in chemistry. Despite its importance, the experimental determination has been limited only to ensemble-averaged techniques. Here, we report a new methodology to evaluate the electronegativity of individual surface atoms by atomic force microscopy. By measuring bond energies on the surface atoms using different tips, we found characteristic linear relations between the bond energies of different chemical species. Using Paulingʼs equation for polar covalent bond, we successfully quantify their electronegativity values. Moreover, we demonstrate that the method is sensitive to variation of the electronegativity of given atomic species on a surface due to different chemical environments. Our findings open up new ways of analyzing surface chemical reactivity in atomic scale.