In a liquid crystal display apparatus having a liquid crystal display panel, an input analog display data is converted to a digital display data, a data portion is selected from the digital display data, and display status information is displayed on the display panel in the form of an overlay display data over the digital display data, so that display adjustment on the display panel is possible. The display adjustment may be automatically performed by use of a minimum value data and a maximum value data, found among the digital display data, for an automatic offset level adjustment and for an automatic gain level adjustment, respectively.