The security information mediation apparatus comprises security information registering unit which registers security information supplied by a client of a user, a transfer unit which transfers the security information registered in the security information registering unit to a client of a program developer. This client judges the usefulness of the security information and outputs reply information when the security information is useful. A reply information registering unit receives the reply information and payment information that indicates payment of the information presentation fee of the corresponding security information from the developer client. A transfer unit transfers the reply information and payment information to the client of the user.