To improve the encoding compressibility of prediction residuals. An encoder performs prediction analysis of input time-series signals to generate prediction residuals expressed by integers, and sets an integer separation parameter that depends on the amplitude of the prediction residuals for each certain time segment. The encoder selects a side information code table corresponding to an index representing the prediction effectiveness of the time-series signals from a set of side information code tables including a side information code table used for variable length coding of side information corresponding to the separation parameter. A decoder selects a side information code table corresponding to the index representing the prediction effectiveness of the time-series signals from a set of side information code tables including a side information code table used for decoding of a code corresponding to the side information corresponding to the integer separation parameter corresponding to the magnitude of the prediction residuals.