An encoder which encodes a picture includes processing circuitry and memory. Using the memory, the processing circuitry: splits the picture into a plurality of slice segments; encodes a plurality of blocks included in each of the plurality of slice segments; reconstructs the plurality of blocks encoded; adds, for each of the plurality of slice segments, control information to a header area of the slice segment, the control information being for controlling application of a filter to the slice segment; and applies, for each of the plurality of slice segments, the filter to a block which has been reconstructed in the slice segment, according to the control information of the slice segment.