Provided are motion vector determining method and apparatus for determining a motion vector via motion vector prediction. The motion vector determining method involves determining a candidate motion vector list comprising motion vectors of a plurality of candidate blocks referred so as to predict a motion vector of a current block, when a reference image of a first candidate block from among the plurality of candidate blocks is different from a reference image of the current block, determining whether or not to use a motion vector of the first candidate block from the candidate motion vector list, based on whether each of the reference image of the current block and the reference image of the first candidate block is a short-term reference image or a long-term reference image, and determining the motion vector of the current block by using a candidate motion vector selected from among the motion vectors comprised in the candidate motion vector list.