Oak wilt caused by Raffaelea quercus-mongolicae was first noticed in South Korea in 2004 and, ever since, its distribution and damage have been increasing. To screen a fungicide effective for oak wilt control by tree injection, laboratory and field experiments were conducted. Ten fungicides and one antibiotic were examined in vivo for their effectiveness in restricting the growth of R. quercus-mongolicae and R. quercivora (Japanese oak wilt pathogen) isolates. To the Korean isolates of R. quercus-mongolicae, chlorothalonil showed the highest fungicidal effects, followed by benomyl and propiconazole. To the Japanese one, propiconazole was highest in the fungicidal effectiveness, followed by benomyl and bitertanol. Propiconazole was selected for field-testing of its control efficacy because it showed good fungicidal effects in vitro and systemic activity. The control efficacy in the field was 87.5% in the first year of injection and 66.7% in the second year, indicating the fungicidal effects last at least over one year.