An electrode in which a silicon layer is provided over a current collector, a thin film layer having a thickness within a certain range is provided on a surface of the silicon layer, and the thin film layer contains fluorine, is used for a power storage device. The thickness of the thin film layer containing fluorine is greater than 0 nm and less than or equal to 10 nm, preferably greater than or equal to 4 nm and less than or equal to 9 nm. The fluorine concentration of the thin film layer containing fluorine is preferably as high as possible, and the nitrogen concentration, the oxygen concentration, and the hydrogen concentration thereof are preferably as low as possible.