Provided are an electronic surveillance system and a method thereof. In the electronic surveillance system that performs electronic surveillance on a subscriber in a communication network, the electronic surveillance system includes: one or more communication service providers that provide retained data, which is information generated while the subscriber uses a communication service; a dedicated storage that stores and manages the retained data provided by the communication service providers; and a law enforcement agency that requests the dedicated storage to send electronic surveillance information on a specific subscriber so as to be provided with the surveillance information when the electronic surveillance information on the specific subscriber is required. Accordingly, retained data, which is subscriber electronic surveillance information is integrally managed and stored in a dedicated storage. Thus, a communication service provider can reduce costs when a law enforcement agency requests subscriber electronic surveillance information. Furthermore, the subscriber electronic surveillance information can be efficiently managed.