Variations occur in the characteristics of transistors. The present invention is a signal-line drive circuit comprising first and second current source circuits corresponding to respective plurality of signal lines, a shift register, and n (n is a natural number of one or more) video-signal constant current source s, wherein each of the first and second current source circuits has a capacitance means and a supply means. The capacitance means held in one of the first and second source circuits converts a current including a current supplied from each of the n video-signal constant current source s to voltage in response to a sampling pulse supplied from the shift register and a latch pulse supplied from the exterior; and the supply means held in the other supplies a current responsive to the converted voltage. The values of the currents supplied from the n video-signal constant current source s are set to a proportion of 20:21: . . . :2n.