A signal processing apparatus comprising: a demultiplexing unit that demultiplexes input encoded data into data including information on a segment including frames in which the same coefficient as a coefficient used in producing a high band signal is selected in a section to be processed including a plurality of frames, and coefficient information for obtaining the coefficient selected in the frames of the segment, and low band encoded data; a low band decoding unit that decodes the low band encoded data to produce a low band signal; a selection unit that selects a coefficient of a frame to be processed based on the coefficient information; a high band sub-band power calculation unit that calculates a high band sub-band power of a high band sub-band signal of each sub-band constituting the high band signal of the frame to be processed based on a low band sub-band power of a low band sub-band signal of each sub-band constituting the low band signal of the frame to be processed and the selected coefficient; and a high band signal production unit that produces the high band signal of the frame to be processed based on the high band sub-band power and the low band sub-band signal; wherein: (a) the section to be processed is such that it has been divided into the segments so that positions of the frames adjacent to each other in which different coefficients are selected are set as boundary positions of the segments, and information indicating a length of each of the segments is set as information on the segments; or (b) the section to be processed is such that it has been divided into the several segments having the same length and information indicating the length of the segments divided into the same length and information indicating whether the selected coefficient is varied before and after each boundary position of the segments are set as information on the segments. a demultiplexing unit that demultiplexes input encoded data into data including information on a segment including frames in which the same coefficient as a coefficient used in producing a high band signal is selected in a section to be processed including a plurality of frames, and coefficient information for obtaining the coefficient selected in the frames of the segment, and low band encoded data; a low band decoding unit that decodes the low band encoded data to produce a low band signal; a selection unit that selects a coefficient of a frame to be processed based on the coefficient information; a high band sub-band power calculation unit that calculates a high band sub-band power of a high band sub-band signal of each sub-band constituting the high band signal of the frame to be processed based on a low band sub-band power of a low band sub-band signal of each sub-band constituting the low band signal of the frame to be processed and the selected coefficient; and a high band signal production unit that produces the high band signal of the frame to be processed based on the high band sub-band power and the low band sub-band signal; wherein: (a) the section to be processed is such that it has been divided into the segments so that positions of the frames adjacent to each other in which different coefficients are selected are set as boundary positions of the segments, and information indicating a length of each of the segments is set as information on the segments; or (b) the section to be processed is such that it has been divided into the several segments having the same length and information indicating the length of the segments divided into the same length and information indicating whether the selected coefficient is varied before and after each boundary position of the segments are set as information on the segments. (a) the section to be processed is such that it has been divided into the segments so that positions of the frames adjacent to each other in which different coefficients are selected are set as boundary positions of the segments, and information indicating a length of each of the segments is set as information on the segments; or (b) the section to be processed is such that it has been divided into the several segments having the same length and information indicating the length of the segments divided into the same length and information indicating whether the selected coefficient is varied before and after each boundary position of the segments are set as information on the segments.