Provided is an image encoding method including generating a first picture reconstructed by using a residual picture and a predicted picture; generating a second picture by applying a first artifact reduction filter to the first picture; determining a picture having a smaller bit-rate distortion cost from among the first and second pictures by comparing a first bit-rate distortion cost of the first picture with a second bit-rate distortion cost of the second picture; generating a third picture by applying an in-loop filter to the determined picture; generating a fourth picture by applying a second artifact reduction filter to the third picture; determining a picture having smaller distortion from among the third and fourth pictures by comparing first distortion of the third picture with second distortion of the fourth picture; and generating, via a processor, a bitstream including information about whether the second artifact reduction filter is applied.