Provided is a method of interpolating an image by determining interpolation filter coefficients. A method of interpolating an image in consideration of smoothing includes differently selecting an interpolation filter based on a sub-pel-unit interpolation location and a smoothness from among interpolation filters for generating at least one sub-pel-unit pixel value located between integer-pel-unit pixels; and generating the at least one sub-pel-unit pixel value by interpolating pixel values of the integer-pel-unit pixels by using the selected interpolation filter.