1. A motion vector estimating method in an encoding method for a moving picture based on a block, the motion vector estimating method comprising: dividing each of a (k−1)-th frame and a k-th frame into blocks, each of which has N×N picture elements, and transforming the blocks by applying an arbitrary transform method; and determining a search area having a size of W×W (here, W>N) in the (k−1)-th frame, finding an N×N block in the search area of the (k−1)-th frame which has an optimal similarity to an N×N block in the k-th frame, and estimating a motion vector by calculating the displacement of the found block.