An electronic endoscope apparatus has a light source, a luminance calculator, a controller, and a brightness adjuster. The light source illuminates an object. The luminance calculator calculates a luminance level indicating a brightness of an object image on the basis of image-pixel signals corresponding to the object image. The controller calculates and outputs a manipulated value in accordance with a luminance-difference between the luminance level and a reference luminance level indicating a standard brightness of the object image. The controller sets a non-sensitive band including a standard point corresponding to the reference luminance level. The brightness adjuster adjusts the brightness of the object image in accordance with the manipulated value. When the manipulated value is inside the non-sensitive band, the controller outputs a non-activating manipulated value so as not to activate the brightness adjuster.