A method and device for detecting an illegal unmanned aerial vehicle (UAV) using a radio wave wall are provided. The method includes generating a radio wave wall between a plurality of reconnaissance UAVs that include a first reconnaissance UAV and second reconnaissance UAVs, using one or more wireless signals transmitted and received between the plurality of reconnaissance UAVs, and determining whether an illegal UAV enters the radio wave wall based on radio signal strengths of wireless signals received from the second reconnaissance UAVs.