An image decoding method may include: receiving a bitstream generated as a result of encoding an image sequence; obtaining, from a sequence parameter set of the bitstream, a first tool set index indicating a tool allowed to decode the bitstream among a plurality of tools; obtaining, from the sequence parameter set, tool flags based on the tool flags, identifying a tool that has been used to encode the image sequence among the plurality of tools; and reconstructing the image sequence based on the identified tool, wherein values of the tool flags are set according to a value of the first tool set index.