The present invention is characterized in that a transistor with its L/W set to 10 or larger is employed, and that |VDS| of the transistor is set equal to or larger than 1 V and equal to or less than |VGS−Vth|. The transistor is used as a resistor so that the resistance of a light emitting element can be held by the transistor. This slows down an increase in internal resistance of the light emitting element and the resultant current value reduction. Accordingly, a change with time in light emission luminance is reduced and the reliability is improved.