Nanometer size particulate matter (PM) emission exhausted from internal combustion engine is one of the major air pollutants, and its reduction technologies are required. In this study, to make clear the influence of flame quenching on PM exhaust, characteristics such as composition, size distribution and density of PM exhausted by metal mesh quenching of laminar diffusion flame with benzene were measured by a combustion type PM analyzer (MEXA-1370PM), a Scanning Mobility Particle Sizer (SMPS) and an electric hydrometer. From these results, it was confirmed that PM emitted from quenched flame included SOF with high mass concentration. Its size was smaller than PM emitted from the normal benzene flame (free flame). Density of PM deposition on the quenched mesh at > 10min was higher than that of PM from free flame, though density of PM emission from quenched flame was lower than that.