The present invention relates to an agent apparatus and method for sharing anonymous identifier-based security information among security management domains. A plurality of security information sharing agent apparatuses respectively located in a plurality of security management domains and configured to collect security information and transmit collected security information to outside of the security management domains. Each security information sharing agent apparatus includes an identifier conversion unit for converting real name identifier-based security information into anonymous identifier-based security information by converting a real name identifier included in the security information into an anonymous identifier, and a security information communication unit for transmitting the anonymous identifier-based security information obtained by the identifier conversion unit to outside of a corresponding security management domain so that security information is shared among the plurality of security management domains.