An apparatus and method for controlling luminance in an liquid crystal display device includes: a liquid crystal display panel having at least two designated areas; at least two lamp units irradiating light the designated areas of the liquid crystal display panel; an arithmetic unit configured to scan image pixels within each of the designated areas of the liquid crystal display panel, to extract a peak value of the gray level of pixels, and to calculate an average peak value for each designated area; and a lamp driver configured to control the lamp units, irradiating light to each designated area, based on the average peak value.