1. An apparatus for encoding a motion vector of a current block into a bitstream, the apparatus including a microprocessor, the microprocessor configured to encode, after the motion vector of the current block is determined, the determined motion vector of the current block, by using a predicted motion vector and a differential motion vector instead of encoding a value of the motion vector of the current block itself, the predicted motion vector being decided from one or more motion vectors of one or more blocks adjacent to the current block, the differential motion vector being derived from a difference between the motion vector of the current block and the predicted motion vector, the microprocessor comprising: a resolution determiner configured to determine a motion vector resolution to be applied to a motion vector of either the current block or an image area in which the current block is located, wherein the motion vector resolution is a fractional pixel precision of a motion vector used for predicting the current block from a reference picture, the fractional pixel precision representing up to which fractional pixel location the reference picture is interpolated; a predicted motion vector calculator configured to decide the predicted motion vector of the current block from the one or more motion vectors of the one or more blocks adjacent to the current block, check whether (i) a motion vector resolution of the predicted motion vector and (ii) the motion vector resolution determined by the resolution determiner are equal to each other, and convert the motion vector resolution of the predicted motion vector such that the converted motion vector resolution of the predicted motion vector is equal to the motion vector resolution determined by the resolution determiner, when the motion vector resolution of the predicted motion vector is different from the motion vector resolution determined by the resolution determiner, wherein the differential motion vector is encoded into the bitstream as a difference between the motion vector of the current block and the predicted motion vector having the converted motion vector resolution; and a mode encoder configured to encode mode information indicating that the differential motion vector is 0, when the differential motion vector is not encoded.