Many researchers have proved that information systems auditing is a very effective tool for improving information systems quality. However, information system auditing in Korea still includes many subjective judgements. This study deals with applying a quantitative model to improve information system auditing quality on security domain. First of all, we have looked at previous researches on information systems audit, especially on security audit. Based on this survey, we have come up with solutions to improve the evaluation efficiency on security audit. We have merged the security audit guidelines of NCA and KISA, and developed a quantified evaluation scheme. We have proved the validity of this model by interviews with experts and by case studies.