A touch panel having high reading accuracy of an object to be detected is provided. In a method for driving a touch panel which is provided with a photo sensor in a pixel, an image is displayed in a display portion of a touch panel, a detection region is determined by detecting approach or contact of an object to be detected in a state in which the image is displayed, and the object to be detected is read while substantially equalizing the intensity of light of pixels in the detection region per unit time and unit area. The intensity of light of the pixels per unit time and unit area, which is to be substantially equal, is preferably the maximum intensity of light in the detection region before adjustment, more preferably, the intensity of light for white display.