A mounting frame combination structure is disclosed, for decreasing a profile thickness of an LCD device, which includes a main support accommodating an LCD panel which may display a picture image or other information, and a backlight provided below the LCD panel; a sash provided above the main support, for retaining the LCD panel and the main support from a front side; a bottom cover provided below the main support and supporting the backlight; and, a mounting frame positioned between the side surfaces of the bottom cover and joined thereto by a fastener. In case a step-difference portion is formed in an outer surface of the sash, the mounting frame is fastened to the main support.