A self light emitting device having a function of correcting drops in brightness in self light emitting elements in a pixel portion, and capable of displaying a uniform image without brightness irregularities, is provided. A specific test pattern is displayed when an electric power source is connected, brightnesses are detected by photoelectric conversion elements arranged in each pixel, and then stored in a memory circuit. A correction circuit then corrects a first image signal based on portions which are insufficient from standard brightnesses (brightnesses of normal self light emitting elements at the same gray stale, stored in advance), and a second image signal is obtained. Display of an image in a display device is performed in accordance with the second image signal.