Abstract Recently, the importance of electrostatic charging state to particle deposition in the human airways has been suggested. In this study, we developed a measurement method of electrostatic charging state of individual ambient aerosol particles using Kelvin probe force microscopy (KPFM). For KPFM substrates, glass plates were more suitable than PTFE or polycarbonate filters. We collected charged polystyrene latex standard particles with the number of elementary charges between 4 to 11 on the glass plate, and measured the topography and the surface potential using KPFM. The difference in surface potential between the particle top and the glass substrate surface was determined as the particle surface potential. The particle surface potential for positively charged particle was＋50 mV and that for negatively charged particle was approximately－45 mV. For the ambient aerosol particles, the surface potential ranged from－56.6 mV to＋156.7 mV, indicating that the number of elementary charges of ambient aerosol particles analyzed in this study was more than 4. Sequential analysis of KPFM followed by SEM/EDX for a single aerosol particle would be useful to find the relationship between the surface potential and chemical composition of individual particles.