Monodisperse particles are useful across a wide range of industrial applications, such as LCD displays, solar cells and rechargeable batteries, due to their uniformly small sizes. However, generating high volumes of monodisperse particles remains challenging. In this study, it was aimed to generate monodisperse aerosols by classifying micrometer-scale solid aerosol particles within a narrow size range. Accordingly, a new particle-size classification device with two virtual impactors connected in series and clean air cores was developed. The first-stage virtual impactor had a slightly larger cutoff size than the second-stage, and the major flow discharged from the first-stage was directed to the second-stage. The target particle size range was altered by changing the nozzle sizes in the first and second stages or by adjusting the flow rate. Subsequently, the classification performance of the two-stage virtual impactor was simulated and validated through an experiment using Arizona test dust. The implemented combinations of cutoff sizes for the first and second stages were 3.0 and 2.0 μm, 3.9 and 2.7 μm, or 6.7 and 4.8 μm. As a result, monodisperse aerosol particles were classified at a geometric standard deviation of 1.04–1.14 and a particle size range of 2–6.7 μm. The two-stage virtual impactor developed herein may be useful for various research and performance evaluations, as it can classify micrometer-scale solid particle aerosols that exhibit high monodispersity.