An image encoding/decoding method and apparatus using coefficients of an adaptive interpolation filter are disclosed including: a coefficient calculator for calculating adaptive interpolation filter coefficient of a current frame; an image encoder for interpolating reference frames using the adaptive interpolation filter coefficient of the current frame and encoding the current frame using the interpolated reference frames; a filter flag encoder for generating and encoding a coefficient-inserted flag or coefficient non-inserted flag as a filter flag according to the adaptive interpolation filter coefficient of the current frame; a coefficient encoder for encoding the adaptive interpolation filter coefficient of the current frame when the filter flag is a coefficient-inserted flag; and a bit stream generator for generating and outputting a bit stream, which includes the encoded current frame and encoded filter flag, and further includes encoded adaptive interpolation filter coefficient of the current frame when the filter flag is the coefficient-inserted flag.