A light balloon-borne aerosol sampler was developed to collect individual stratospheric aerosol particles in order to analyze the composition by electron microscopy. The sampler, which is 917 g in weight, consists of a two-stage impactor, a pump and a control unit. The sampler can be easily lifted using a rubber balloon of 3 kg in weight and be recovered in rural areas by predicting the accurate falling points. This sampler can fix the position of an electron microscopic grid just below the impactor jet during each collection. During an observation, 16 samples in each impactor stage can be collected. Aerosol samples from the ground to the lower stratosphere were obtained by using this sampler in August 1994 over Tsukuba, Japan. Results on the observation of stratospheric particles showed that sulfuric acid particles were dominant in particles of radius between 0.03 and 1 μm. As compared with a single-stage impactor used in our previous observations, the use of the two-stage impactor could reduce the overlap of the satellite droplet rings formed by sulfuric acid particles on the collecting surface which masked smaller particles. The samples collected by this sampler are useful to examine the composition of individual particles in a wide size range by electron microscopy.