PURPOSE: To decrease the number of reference voltages to be smaller than the number of gradations of display without complicating a peripheral circuit and to make multilevel image even when the packaging space of drivers on the data line side is limited by outputting a gradation signal of a voltage value of averaged reference voltage values selected corresponding to the respective digital video signal groups.

CONSTITUTION: Respective decoder circuits 21, 22 select one reference voltage from a reference voltage source of the reference voltage group 23 composed of reference voltages V11-V1A supplied from a generating source and of a reference voltage group 24 composed of reference voltages V21-V2B in accordance with an inputted digital video signal by means of analog switches SW11-SW1A, SW21-SW2B, respectively. The voltage value on X point is the averaged value between two reference voltages selected from the reference voltage groups 23, 24 by means of the ON resistance of analog switches of one among the switches SW11-SW1A and one among switches SW21-SW2B modes turned on by means of the decoder circuits 21, 22, respectively.