A device for adjusting the exposure of an image sensor includes an average luminance value calculation unit, a first exposure control unit and a correction exposure value calculation unit. The average luminance value calculation unit calculates the first total average luminance value of pixels that are output from the image sensor. The first exposure control unit controls the exposure value of the image sensor based on a previously set exposure value. The correction exposure value calculation unit calculates a correction exposure value by multiplying the exposure value, which is previously set on the first exposure control unit, by the ratio of a target luminance value to the first total average luminance value. Additionally, the first exposure control unit receives the correction exposure value from the correction exposure value calculation unit and controls the exposure value of the image sensor based on the correction exposure value.