In this study, we propose a polarization-interferometric nonlinear confocal microscope for analyzing DDS (drug delivery system) nanoparticle. This microscope is composed of a usual confocal microscope and a polarization interferometer imitating the Michaelson interferometer. In addition, scanning with MEMS mirrors provides high contrast resolution measurement. We have measured three-dimensional images of a single polystyrene particle with the microscope proposed.