In a data line driver for driving data lines of a display apparatus, a data register is adapted to latch video data and a definite non-video gradation data via a data bus. A data latch circuit is adapted to latch the video data and the definite non-video gradation data at different timings to generate digital output signals. A digital/analog converter is adapted to convert the digital output signals of the data latch circuit into analog signals. An output buffer is adapted to apply the analog signals of the digital/analog converter to the data lines.