A device and method for controlling a brightness of an image signal in a moving picture transmission/reception system is disclosed. The present invention includes a control point detecting unit for receiving an image, calculating a Cumulative Density Function from two most significant bits of the image, dividing an axis into a required number of portions, and detecting a required number of control points. The present invention also includes an image signal brightness controlling unit for calculating and dividing six least significant bits of the image and a signal from the control point detecting unit for controlling a next frame of the image.