There are many reports on the in situ remote measurement by the LLS (laser light scattering) method for the spatial distribution of particles that are generated in the gas phase during the RF (radio frequency) plasma-processing. However, almost every report is limited to high-concentration particle clouds trapped at a plasma/ion sheath boundary region, since it is difficult to measure low-concentration particles by the LLS method. In this study, a sampling pipe was inserted into an RF plasma reactor to suck out test SiO2 particles fed from the outside of the reactor, and particles suspended in various positions were measured with a particle counter, which is operable under low-pressure conditions. This technique allows measurement of the distribution of low-concentration particles that cannot be achieved by the LLS method. Measurement of the process conditions under which particle-trapping clouds are formed in the plasma region revealed that particles overfed into the clouds did not flow out downward to the grounded electrode (substrate), but flowed out of the plasma region in the radially outward direction of the RF electrode. It was also found that the range of feeding gas flow rate in which the formation of particle clouds was hindered and thus particles flowed directly toward the grounded electrode depended on RF power and particle diameter. Furthermore, measurements of transport of trapped particles in the postplasma process suggested possible conditions under which particle contamination of substrate surfaces is likely to occur.