an electron beam system using a scanning electron microscope equipped with a function for controlling a charged state of a sample to be observed includes electron optics for obtaining image data of the scanning electron microscope , and a monitor that displays a relationship between an equation for determining a degree of separation of peaks which appear in a histogram obtained on a basis of the image data and at least one parameter among parameters for controlling the charged state of the sample . an optimized parameter for controlling the charged stage of the sample can be visually distinguished on the monitor .