A driving method of a semiconductor device that takes three-dimensional images with short duration is provided. In a first step, a light source starts to emit light, and first potential corresponding to the total amount of light received by a first photoelectric conversion element and a second photoelectric conversion element is written to a first charge accumulation region. In a second step, the light source stops emitting light and second potential corresponding to the total amount of light received by the first photoelectric conversion element and the second photoelectric conversion element is written to a second charge accumulation region. In a third step, first data corresponding to the potential written to the first charge accumulation region is read. In a fourth step, second data corresponding to the potential written to the second charge accumulation region is read.