The display apparatus includes an AD converter (6) converting an analog video signal into a digital video signal, a phase adjuster (1) and a horizontal start position detector (7). The detector detects a horizontal start position where an output value of the AD converter becomes a minimum value that exceeds a threshold level in a video horizontal direction. The phase adjuster acquires a start position change phase where the horizontal start position is changed. The phase adjuster calculates a first phase period where the analog video signal starts its transition from a first level to a second (higher) level and then ends the transition. The phase adjuster sets a phase not included in the first phase period as an adjusted phase of the quantization clock.