Photoinduced changes in surface interactions were studied using surface forces measurement. Surfaces were modified by the Langmuir-Blodgett (LB) deposition of a mixed monolayer of a spiropyran derivative (SP1822) and n-octadecane (C18). The LB film exhibited a reversible change in its structure between the SP form (neutral closed form) and the PMC form (zwitterionic open form) upon irradiation by light at specific wavelengths, which were confirmed by UV-VIS spectroscopy. A long-range attraction extending to ca. 100 mn was observed for the surfaces containing the PMC forms, while an interaction between the SP forms was repulsive in the long-range and attractive at distances less than 20 nm.