A spark discharge aerosol generator has been applied to nanoparticle production. However, the byproducts such as ozone, nitric oxide and nitrogen dioxide were generated simultaneously with particles in air. In this study, the generation characteristics of byproduct gas were investigated for the air flow rates and the applied discharge power in spark discharge. The results show that NOx concentration increases linearly with discharge energy. However, ozone concentration increases with discharge energy in low energy region, but decrease adversely with discharge energy in high energy region.