1. A video encoding method in a temporal direct mode in a hierarchical structure, comprising: obtaining a temporal position of at least one of a forward reference frame and a backward reference frame of a high-pass frame; searching for at least one frame which exists at the temporal position and has motion vector information; finding plural frames for at least one high pass frame and selecting as a co-located frame a frame, among the plural frames, having a motion vector of which an interval is closest to a difference in interval between the forward reference frame and the backward reference frame of the high-pass frame, and extracting the motion vector of the selected frame; and encoding information on the selected frame, wherein the interval of the motion vector is a difference between a picture order count (POC) of a frame which has the motion vector and a POC of a frame which is referred to by the motion vector, wherein the difference in interval between the forward reference frame and the backward reference frame of the high-pass frame is a difference of a POC of the forward reference frame of the high-pass frame and a POC of the backward reference frame of the high-pass frame, and wherein the selecting of the co-located frame comprises determining which frame among the plural frames has the motion vector, the interval of which has a POC difference that is closest to the difference of the POC of the forward reference frame of the high-pass frame and the POC of the backward reference frame of the high-pass frame.