A scan format converter for converting a video format by bi-sigmoid interpolation. In the scan format converter, a memory controller has a look-up table at which first and second displacement values for pixel points of a video format to be converted are stored, controls transmission of color signals input from an external device, and reads the first and second displacement values for the pixel points of the color signals from the look-up table. A mode detector detects horizontal and vertical sync signals input from the external device and outputs a video format detection signal representing a mode of the currently input video format to the memory controller. A memory temporarily stores the color signals. A color signal logic circuit has a plurality of bi-sigmoid interpolation tables at which sigmoid interpolation values according to a color signal level difference between two pixel points are stored, and bi-sigmoid-interpolates the color signal levels of the input pixel points with respect to an x-axis and a y-axis according to the first and second displacement values input from the memory controller. A sync generator generates a sync signal to the color signal logic circuit.