A loop filtering method and apparatus are provided. The loop filtering method includes: calculating blocking effect strength based on coding type information, which specifies the coding type of a block to be filtered, a motion vector of the block, and reference frame information, which identifies a reference frame; determining a filtering unit to be used for filtering the block based on the calculated blocking effect strength; and performing filtering on the block using the determined filtering unit. Accordingly, it is possible to provide high-quality HDTV images by determining whether to perform loop filtering and adjusting the degree of loop filtering in consideration of the characteristics of HDTV images.