A method for a stage device of an electron beam exposure system which conducts a cleaning operation and an electron beam (EB) exposure operation is disclosed. The method includes the steps of moving a movable stage within a predetermined range and regulating pressure of gas supplied to an air bearing; and setting a floating height of the movable stage in the cleaning operation lower than that in the EB exposure operation and setting the pressure in a differential pumping portion in the cleaning operation equal to that in the EB exposure operation, or setting the floating height of the movable stage in the cleaning operation equal to that in the EB exposure operation and setting the pressure in the differential pumping portion in the cleaning operation higher than that in the EB exposure operation.