Scanning near-field optical microscopy (SNOM) combined with Kelvin force microscopy (KFM) using a microfabricated force-sensing cantilever with a lead zirconate titanate (PZT) thin film as an integrated deflection sensor have been developed. We applied the frequency modulation (FM) detection method to this setup to increase the detection sensitivity of electrostatic forces between a probe tip and a sample. Latex particles dispersed in a polyvinylalcohol (PVA) thin film deposited onto a glass substrate were stably imaged with the SNOM while both local optical and electrical properties of a ferroelectric thin film were successfully investigated.