A drive waveform signal which is level controlled by discontinuous levels including a minimum level corresponding to luminance brightness gradation data which is not 0, at least one non-minimum level corresponding to larger luminance brightness gradation data, and an intermediate level between the minimum and non-minimum level. The signal, which is employed to drive an image display unit, is given pulse width control with discontinuous pulse width, and has a portion, controlled with the minimum level, in its trailing edge, and a portion, controlled with the intermediate level just before the former portion, when it has the portion controlled by the non-minimum level.