PURPOSE: A user interface method of displaying an important alarm and changing over a process screen of a supervisory control system is provided to quickly move to the desired process screen using a menu button module. CONSTITUTION: A menu button module of a two-level tree structure for changing a process scene is marked on the upper end or the bottom of a HMI(Human Machine Interface) screen. The menu button module includes a plurality of group buttons which are an upper level and a plurality of screen buttons which are a lower level. The name of the process screen corresponding to a selected specific group button is marked on the screen button of the lower level when a user selects the specific group button.
