A private network service providing method and system for breaking dependency on a terminal and providing a private network service is provided. The private network service system according to the present exemplary embodiments include: a service linkage server for, when access to a private network is requested by a mobile communication terminal connected to a public network or access of the mobile communication terminal to the private network is requested by a third server, identifying identification information of the mobile communication terminal and requesting an access point name-operator identifier (APN-OI) change to a home subscriber server; the home subscriber server for authenticating whether the mobile communication terminal is subscribed to a private network service when the APN-OI change is requested by the service linkage server, and identifying an access point name (APN) included in a subscriber profile of the mobile communication terminal and changing a public APN-OI recorded in the APN to a private APN-OI when the authenticating is successful; and a mobility management entity for receiving the subscriber profile of the mobile communication terminal from the home subscriber server when there is an attempt of access from the mobile communication terminal, and inducing the mobile communication terminal to connect to a public gateway or a private gateway, using an IP address of the public gateway or IP address of the private gateway corresponding to the APN included in the subscriber profile.