A restoring picture filtering method performed by a decoding device, according to the present invention, comprises the steps of: calculating the activity of an image of a target region of a restoring picture; determining the directivity of the image of the target region; selecting a particular filter within a filter set on the basis of the activity and the directivity; and performing filtering on the restoring picture on the basis of the selected filter. According to the present invention, adaptive filtering may be applied on the basis of image properties of a target block of a restoring picture, and the objective/subjective image quality of the restoring picture may be enhanced therethrough.