The present invention relates to a frequency band extending device and method, an encoding device and method, a decoding device and method, and a program, whereby music signals can be played with higher sound quality due to the extension of frequency bands.A bandpass filter 13 divides an input signal into multiple sub-band signals, a feature amount calculating circuit 14 calculates feature amount using at least one of the multiple divided sub-band signals and the input signal, a high frequency sub-band power estimating circuit 15 calculates an estimated value of a high frequency sub-band power based on the calculated feature amount, a high frequency signal generating circuit 16 generates a high frequency signal component based on the multiple sub-band signals divided by the bandpass filter 13, and the estimated value of the high frequency sub-band power calculated by the high frequency sub-band power estimating circuit 15. A frequency band extending device 10 extends the frequency band of the input signal using a high frequency signal component. The present invention may be applied to a frequency band extending device, for example.