1. A motion prediction apparatus comprising: a similarity detector that detects block similarities indicating degree of similarities between a pixel block in a current frame and pixel blocks in a next frame; a smoothness detector that detects smoothness level of the pixel block in the current frame, the smoothness level indicating smallness of an image variance of the pixel block; a weighting unit that applies weights to each of the block similarities based on the smoothness level; and a motion vector determination unit that determines a motion vector of the pixel block in the current frame based on the weighted block similarities.