A method of determining a reference picture set (RPS), which is a set of reference pictures used in predictive decoding of a current picture that is to be decoded includes: obtaining a flag indicating whether the RPS is determined based on POC values of the current picture and a previous picture or whether the RPS is determined based on an index of a reference RPS, which is an identification value of the reference RPS that is one of pre-defined RPSs and is referred to in determining the RPS, and a delta RPS that is a difference value between a POC vale of a reference picture included in the reference RPS and a POC value of a reference picture included in the RPS; and determining the RPS according to a value of the flag.