1. A video encoding method comprising: determining whether a current block includes an affine-transformation object having an affine transformation; if the current block includes an affine-transformation object, generating a prediction block by performing affine transformation-based motion compensation on the current block in consideration of an affine trans-formation of the affine-transformation object; and if the current block does not include any affine-transformation object, generating a prediction block by performing motion vector-based motion compensation on the current block using a motion vector of the current block.