The present invention relates to the field of display technology, and in particular to an apparatus and a method for improving uneven display brightness, and a display device. The apparatus for improving uneven display rightness includes: a division module configured to divide a display region into a plurality of segmented regions in a scanning line direction; a collection module configured to collect display brightness of the respective segmented regions; a comparison module configured to set reference brightness in a current grayscale according to the collected display brightness of the respective segmented regions; and an adjustment module configured to adjust the display brightness in the current grayscale of each segmented region according to the reference brightness in the current grayscale and the display brightness of each segmented region, so as to reduce the differences in the display brightness in the current grayscale among the respective segmented regions.