In this study, the concentration of fine dust particles and the size distribution of fine dust particles were analyzed by measuring the dust generated during the cleaning process of an indoor office. We measured PM10, PM2.5, and PM1.0 and analyzed the size distributions of dust bigger than 0.3 μm in diameter during cleaning. The results showed that the concentration of PM10 increased rapidly during cleaning, and PM1.0 did not increase. Before cleaning with a broom, the fine dust concentration was about 50 μg m–3, but increased to about 400 μg m–3 as cleaning progressed. In the case of indoor cleaning with a vacuum cleaner, the concentration of PM10 increased during the cleaning process and the increase of PM2.5 was relatively small. PM1.0 did not increase as in the case of cleaning with the broom.