The present disclosure in one or more embodiments provides a scan converter, an ultrasound diagnostic apparatus, and a method capable of performing real-time interpolation without directional distortion. An embodiment of the present disclosure prevents directional distortion of velocity data by performing vector interpolation by using a weight according to distances of four adjacent complex signals in color flow-mode (C-mode) and achieves real-time scan conversion by constructing a lookup table for vector interpolation.