The invention provides a light emitting device using transistors manufactured by the conventional process while reducing an area occupied by capacitors, whereby variations in luminance of light emitting elements caused by variations in gate voltage Vgs of the transistors are suppressed, and a luminance decay of the light emitting elements due to the degradation of light emitting materials and variations in luminance can also be suppressed. The light emitting device includes a first transistor for controlling a video signal input to a pixel, second and third transistors one of which is turned ON while the other is turned OFF according to a potential of the video signal, and a fourth transistor for supplying current to a light emitting element according to each drain potential of the second and third transistors, wherein the drains of the second and third transistors are connected to each other, the third and fourth transistors have the same conductivity, and the sources of the third and fourth transistors are connected to each other.