Disclosed are a communication method for merging, with IoT technology, a 5G communication system for supporting a data transmission rate higher than that of a 4G system, and a system therefor. The disclosure can be applied to intelligent services (for example, smart home, smart building, smart city, smart car or connected car, health care, digital education, retail business, security and safety related services, and the like) on the basis of 5G communication technology and IoT-related technologies. According to various embodiments of the disclosure, a method for authenticating a smart key of an electronic device comprises the steps of: transmitting an authentication request in a predetermined cycle; receiving authentication responses from a smart key device; determining whether there is a relay attack on the basis of the interval of the received authentication responses; and authenticating the smart key device when it is determined that there is no relay attack. However, the disclosure is not delimited to the embodiment above, and other embodiments are possible.