A head mounted display (HMD) apparatus and a display method thereof are provided. The apparatus includes a display configured to provide an image, an active element comprising a plurality of micro-mirrors and configured to reflect the image provided on the display, and a processor configured to detect a user's eyesight and adjust a focal length of the image provided on the display by controlling a gradient of at least some of the plurality of the micro-mirrors based on the detected user's eyesight.