An apparatus and a method of smoothing the brightness of an image photographed in an image sensor without amplifying a noise component of a surrounding part of the image are disclosed. The image brightness correction apparatus correcting the brightness of an image by using a correction curve can include an image input unit, receiving an image; a correction gradient selection unit, selecting a gradient of the correction curve corresponding to an object pixel, having the brightness desired to be corrected, of pixels of the image; a correction performance unit, converting original brightness of the object pixel into correction brightness according to the correction curve having the selected gradient; and an image output unit, outputting the image allowing the object pixel to have the correction brightness by the correction performance unit; whereas the correction curve increases the contrast of the corresponding correction brightness if the original brightness is the same as or smaller than a predetermined brightness, and the correction curve decreases the contrast of the corresponding correction brightness if the original brightness is larger than a predetermined brightness. With the present invention, a dynamic range of an image is smooth and the contrast of the image is acquired.