In order to industrialization of the entomopathogenic nematode (EPN) isolated in Korea, it is necessary to switch to infective juveniles. Since the conversion to infective juveniles in the end of solid culture is important against the outside environment, it has a great influence on insecticidal efficacy and shelf life. We investigated whether the concentration of CO2 and NH3 at the end of the solid culture was artificially increased to affect the infective juvenile induction rate. Optimal exposure time for conversion to infective juveniles was 5 minutes for CO2 and 3 minutes for NH3. Optimal treatment time was 9 days after EPN inoculation for both CO2 and NH3. And optimum concentration was 80~90% for both CO2 and NH3 for EPN infective juveniles stage conversion.