The present disclosure relates to a method and apparatus for improving the encoding efficiency by adaptively changing the resolution of the motion vector in the inter prediction encoding and inter prediction decoding of a video. The video encoding/decoding apparatus includes: a video encoder for determining a motion vector resolution of each area or motion vector of a video and performing an inter prediction encoding of the video by using a motion vector according to the motion vector resolution determined for each area or motion vector; and a video decoder for reconstructing a resolution by extracting resolution information from a bitstream, and then performing an inter prediction decoding by using a motion vector according to the motion vector resolution of each reconstructed area or motion vector.