The apparatus for detecting arc occurred in chamber for plasma treatment used for manufacturing semiconductor or LCD panel comprises, a sensor module for sensing the arc; a processor module for processing data from the sensor module; wherein the sensor module includes RGB color sensor for sensing color data of the arc occurred in the chamber, the RGB color sensor is a sensor sensable at least one of red color or green color or blue color of the arc, the apparatus detects the arc by sensing data of color and chroma and brightness of the arc.