Provided is an image encoding/decoding apparatus and method. The image encoding apparatus may include a motion vector prediction unit to perform a prediction with respect to an arbitrary motion vector of a current block within an image, using at least one of vector information of a motion vector corresponding to an adjacent block and vector information of a previous motion vector of the current block, and a differential determination unit to determine differential information of a motion vector of the current block based on the motion vector predicted in the motion vector prediction unit and an actual motion vector of the current block.