1. A motion compensated interframe prediction method comprising the steps of: setting plural representative points at positions in a frame or at positions which are outside and in the neighborhood of the frame; detecting first motion vectors at the representative points; dividing the frame into plural areas for which a motion vector interpolating method is adaptively selected; generating first interpolated motion vectors by interpolating, for each area of the plural areas, the first motion vectors on the basis of the representative points on a boundary of an area or on the basis of the representative points contained in the area and areas adjacent thereto; detecting second motion vectors for each area of the plural areas separately from the representative points on the boundary of the area or contained in the area and areas adjacent thereto; generating second interpolated motion vectors for each of the plural areas by interpolating the detected second motion vectors; adaptively selecting either the first interpolated motion vector or the second interpolated motion vector for each area of the plural areas based on which of the first or second interpolated motion vectors requires the least amount of additional coding, wherein said adaptively selecting step selects the first interpolated motion vector interpolating method only when it is expected that the prediction performance can be enhanced to the extent that it offsets an increase of an additive coding amount; and performing motion compensated interframe prediction for each area of the plural areas on the basis of the selected interpolated motion vectors.