A variety of semi-volatile organic chemicals (SVOCs), such as plasticizers and flame retardants, are released into indoor air and dust from building materials, furniture, and housekeeping products in residential housing. In this study, we measured 58 SVOCs in indoor air and dust from 50 and 48 dwellings, respectively, from 19 prefectures across Japan during the hot season (from July to September). In order to reveal the current situation regarding these compounds in indoor air, we obtained indoor air samples using a newly designed four-stage multi-nozzle cascade impactor and measured the concentrations of the chemicals in the indoor air in three different particle size ranges (10μm), as well as a gas phase. From the results obtained using the multi-nozzle cascade impactor, smaller compounds were mainly detected in the gas phase and larger compounds were found in the particle phases. However, the three cyclic polysiloxanes, including decamethylcyclooctasiloxane (D5), with large molecules were detected in the gas phase in all of the houses. Among the 58 chemicals, D5 showed the highest median concentration (1.1 μg/m³) in the range from 0.2 to 36 μg/m³ in the indoor air samples. Our analysis of house dust revealed that di-2-ethylhexyl phthalate (DEHP) was present in all samples at the highest median concentration (590 μg/g) in the range from 200 to 6,200 μg/g. These results suggest that the residential indoor environment in Japan is mainly polluted with siloxanes in the gas phase of indoor air and by DEHP in house dust.