An electronic endoscope apparatus has a light source, a pixel luminance detector, a division setter, an average block luminance calculator, a peak-luminance determiner, a representative luminance calculator, and a brightness adjuster. The division setter divides the subject image into a plurality of blocks composed of given pixels. The average block luminance calculator calculates a plurality of average block-luminance-levels. The peak-luminance determiner compares the average block-luminance-levels with each other in order to determine a substantially maximum average block-luminance-level from the plurality of average block-luminance-levels as a peak luminance level. The representative luminance calculator calculates a representative luminance level indicating a brightness of the subject image. The brightness adjuster adjusts the brightness of the subject image in accordance with the representative luminance level.