1. An electronic device comprising: a storage configured to store domain information that is categorized for dialogue subjects; a speaker configured to output a system response based on a user utterance sound; and a processor configured to: detect a domain, among the domain information, based on the user utterance sound, determine one among the detected domain and a previous domain as a domain to be used to process the user utterance sound, based on a confidence between the user utterance sound and the detected domain, and process the user utterance sound to generate the system response, based on the determined domain.