Provided is an encoding device which can suppress quality degradation of a decoded signal in a band extension for estimating a high range from a low range of a decoded signal. The encoding device includes: a first layer encoding unit (202) which encodes the low-range portion of an input signal to generate first encoded information; a first layer decoding unit (203) which decodes the first encoded information to generate a decoded signal; a second layer encoding unit (206) which estimates a high-range portion of the input signal from the decoded signal so as to generate an estimated signal and generate second encoded information to obtain the estimated signal; a peak feature analysis unit (207) which obtains a difference in a wave adjustment structure between the high-range portion of the input signal and the estimated signal or the low-range portion of the input signal; and an encoding information multiplexing unit (208) which integrates the first encoded information, the second encoded information, and the difference in the wave adjustment structure.