A video decoding method comprising: obtaining, from a part of a bitstream about a sequence parameter set, the number of short term reference picture sets included in the part of the bitstream about the sequence parameter set; determining whether a current index of a short term reference picture set is equal to the number of short term reference picture sets included in the part of the bitstream about the sequence parameter set; when the current index of the short term reference picture set is equal to the number of short term reference picture sets, obtaining, from the bitstream, delta index information about a difference between the current index of the short term reference picture set and an index of a reference short term reference picture set, information about a sign of a delta RPS and information about an absolute value of the delta RPS; determining the index of the reference short term reference picture set which indicates the reference short term reference picture set based on the delta index information and the current index of the short term reference picture set, wherein the index of the reference short term reference picture set is smaller than the current index of the short term reference picture set; determining the delta RPS based on the information about the sign of the delta RPS and the information about the absolute value of the delta RPS; determining delta picture order count values between picture order count values of reference pictures included in a current short term reference picture set and picture order count value of the current picture by adding each delta picture order count value between picture order count value of reference picture in the reference short term reference picture set which is identified by the index of the reference short term reference picture set and the picture order count value of the current picture to the delta RPS; and determining POC values of the reference pictures included in the current short term reference picture set based on the picture order count value of the current picture and the delta picture order count values between the picture order count values of the reference pictures included in the current short term reference picture set and the picture order count value of the current picture, wherein the current index of the short term reference picture set being equal to the number of short term reference picture sets indicates the short term reference picture set regarding the current index is not defined in the sequence parameter set and is defined in a slice header obtaining, from a part of a bitstream about a sequence parameter set, the number of short term reference picture sets included in the part of the bitstream about the sequence parameter set; determining whether a current index of a short term reference picture set is equal to the number of short term reference picture sets included in the part of the bitstream about the sequence parameter set; when the current index of the short term reference picture set is equal to the number of short term reference picture sets, obtaining, from the bitstream, delta index information about a difference between the current index of the short term reference picture set and an index of a reference short term reference picture set, information about a sign of a delta RPS and information about an absolute value of the delta RPS; determining the index of the reference short term reference picture set which indicates the reference short term reference picture set based on the delta index information and the current index of the short term reference picture set, wherein the index of the reference short term reference picture set is smaller than the current index of the short term reference picture set; determining the delta RPS based on the information about the sign of the delta RPS and the information about the absolute value of the delta RPS; determining delta picture order count values between picture order count values of reference pictures included in a current short term reference picture set and picture order count value of the current picture by adding each delta picture order count value between picture order count value of reference picture in the reference short term reference picture set which is identified by the index of the reference short term reference picture set and the picture order count value of the current picture to the delta RPS; and determining POC values of the reference pictures included in the current short term reference picture set based on the picture order count value of the current picture and the delta picture order count values between the picture order count values of the reference pictures included in the current short term reference picture set and the picture order count value of the current picture, wherein the current index of the short term reference picture set being equal to the number of short term reference picture sets indicates the short term reference picture set regarding the current index is not defined in the sequence parameter set and is defined in a slice header