A wireless LAN relay system is designed to extend the transmission range while maintaining stable communication. In this paper, we propose a wireless LAN relay system using multicopter unmanned aerial vehicles (UAVs) and evaluate the communication performance. For the demonstration experiment, we employ air-to-air and ground-to-air communications, where the former is a link between UAVs, and the latter is a link between a UAV and ground node. We measure the throughput and the received signal strength indicator, and clarify the communication performance of the wireless LAN relay system.