The previous microelectrochemical measurement system based on the micro-electrode technique with a glass capillary dramatically advanced our understanding of pitting corrosion over the past ten years. However, by using this system, it was impossible to take in-situ and real-time observations of dissolving surfaces. Here we developed a measurement system for in-situ and real-time observations (lateral resolution: ca. 350 nm, time resolution: 30 images/s) of the initiation processes of pitting corrosion on stainless steel by combining an optical microscope with a microelectrochemical cell. The results of the observations on pit initiation at the manganese sulfide (MnS) inclusions clearly indicated marked differences in the initiation processes of metastable and stable pits. The experimental technique developed here is applicable to a wide range of the local electrochemical analysis of electrode surfaces.