The present invention relates to a server-client type online game operation device. A remote control device for user interface includes : a storage unit in which a plurality of graphic user interface (GUI) application programming interfaces (API) which are application programs using GUI in a game provided by a game server; and a GUI relay server which receives packet data for data operation in a game from a smart device, calls or updates one or more among the GUI APIs stored in the storage unit, provides the game server with the APIs, and provides GUIs displayed on the smart device and GUIs displayed on a game client.(110) Authentication server(210) Storage unit(220) Relay server(310) User interface of an application for smart devicesCOPYRIGHT KIPO 2015