1. A method of converting an interlaced video signal to a progressive video signal, the method comprising: estimating motion vectors of a field to be interpolated and an accuracy of the motion vectors using motion vectors of adjacent fields of the video signal; determining existence or non-existence of global motion by analyzing the estimated motion vectors; generating a pixel to be interpolated by a first method which performs motion compensation with respect to the field to be interpolated using at least one of the estimated motion vectors; generating the pixel to be interpolated by a second method which uses pixels adjacent to the pixel to be interpolated in the field to be interpolated and pixels adjacent to the pixel to be interpolated in the fields preceding and succeeding the field of the pixel to be interpolated; and selectively outputting one of the pixel generated by the first method or the pixel generated by the second method according to the estimated accuracy of the at least one estimated motion vector and the determined existence or non-existence of global motion.