4. The interesting section identifying device of claim 3 , wherein the reference index calculating unit is further configured to calculate a threshold Euclidean distance as a Euclidean distance from the reference vector to a second unit section frequency vector having a greatest Euclidean distance from the reference vector among a plurality of second unit section frequency vectors included in the reference section, and the interesting section candidate extracting unit initially designates the reference section as a temporary interesting section candidate and repeats a process of (i) determining whether the Euclidean distance from the reference vector to the second unit section frequency vector of the second unit section adjacent to the temporary interesting section exceeds the threshold Euclidean distance and (ii) including the second unit section adjacent to the temporary interesting section candidate in the temporary interesting section candidate when determining that the Euclidean distance does not exceed the threshold Euclidean distance, the interesting section candidate extracting unit terminating repetition of the process and designating the temporary interesting section candidate as the interesting section candidate upon determining that the Euclidean distance exceeds the threshold Euclidean distance.
4. The interesting section identifying device of claim 3 , wherein the reference index calculating unit is further configured to calculate a threshold Euclidean distance as a Euclidean distance from the reference vector to a second unit section frequency vector having a greatest Euclidean distance from the reference vector among a plurality of second unit section frequency vectors included in the reference section, and the interesting section candidate extracting unit initially designates the reference section as a temporary interesting section candidate and repeats a process of (i) determining whether the Euclidean distance from the reference vector to the second unit section frequency vector of the second unit section adjacent to the temporary interesting section exceeds the threshold Euclidean distance and (ii) including the second unit section adjacent to the temporary interesting section candidate in the temporary interesting section candidate when determining that the Euclidean distance does not exceed the threshold Euclidean distance, the interesting section candidate extracting unit terminating repetition of the process and designating the temporary interesting section candidate as the interesting section candidate upon determining that the Euclidean distance exceeds the threshold Euclidean distance. 5. The interesting section identifying device of claim 4 , wherein the detailed structure determining unit determines whether the detailed structure is included in an initial second unit section or a final second unit section of the interesting section candidate, and the interesting section identifying unit identifies a starting point of the interesting section by analyzing the initial second unit section when the detailed structure is determined to be included in the initial second unit section, and identifies an ending point of the interesting section by analyzing the final second unit section when the detailed structure is determined to be included in the final second unit section.