This invention provides a display device in which it is possible to have a light emitting element emitted light with constant luminance without coming under the influence of deterioration over time, and it is possible to realize accurate gray scale express, and yet, it is possible to speed up writing of a signal current to each pixel, and influence of noise of a leak current etc. is suppressed, and a driving method thereof. A plurality of pairs of switch portions and current source circuits are disposed in each pixel. Switching of each of a plurality of the switch portions is controlled by a digital video signal. When the switch portion is turned on, by a current supplied from the current source circuit making a pair with the switch portion, the light emitting element emits light. A current which is supplied from one current source circuit to the light emitting element is constant. A value of a current flowing through the light emitting element is comparable to a value of added currents which are supplied to the light emitting element from respective all current source circuits making pairs with the switch portions which are in the conductive states.