A method which calculates a motion vector based on a transformed picture obtained by Discrete Coefficient Transform (DCT) or a Wavelet transform, and an apparatus appropriate for the method. The motion vector estimating method in an encoding method for a moving picture based on a block, the motion vector estimating method includes dividing each of a (k-1)-th frame and a k-th frame into blocks, each of which has N.times.N picture elements, and transforming the blocks by applying an arbitrary transform method; and determining a search area having a size of W.times.W (here, W>N) in the (k-1)-th frame, finding an N.times.N block in the search area of the (k-1)-th frame which has an optimal similarity to an N.times.N block in the k-th frame, and estimating a motion vector by calculating the displacement of the found block.
