An ultrasonic observation apparatus for transmitting an ultrasonic wave to a subject, receiving the ultrasonic wave reflected by the subject, and determining a tissue property of the subject based on an analysis result of the frequency spectrum of the received ultrasonic wave, the ultrasonic observation apparatus comprising: a frequency analyzer configured to calculate a frequency spectrum by analyzing a frequency of the received ultrasonic wave received from a specified reception depth; a frequency band information storage unit that stores, for each reception depth, frequency values as upper limits of frequency bands in a plurality of reception depths; a frequency band setting unit configured to set a frequency band of the frequency spectrum in the specified reception depth, calculated by the frequency analyzer, based on a frequency value in the specified reception depth among the frequency values stored in the frequency band information storage unit; a reference spectrum information storage unit that stores, for each reception depth, reference spectra in the plurality of reception depths obtained based on frequencies of ultrasonic waves received from a reference reflector; a corrected frequency spectrum calculator configured to calculate a corrected frequency spectrum by correcting the frequency spectrum calculated by the frequency analyzer based on the reference spectrum in the specified reception depth among the reference spectra stored in the reference spectrum information storage unit; and a feature data extracting unit including an approximating unit configured to perform an approximating process only on a part of the corrected frequency spectrum calculated by the corrected frequency spectrum calculator, the part of the corrected frequency spectrum being included in the frequency band set by the frequency band setting unit, the feature data extracting unit being configured to extract feature data indicating the tissue property of the subject using a result of the approximating process performed by the approximating unit; wherein the frequency band setting unit is configured to set the frequency band which is used when the approximating unit performs the approximating process. a frequency analyzer configured to calculate a frequency spectrum by analyzing a frequency of the received ultrasonic wave received from a specified reception depth; a frequency band information storage unit that stores, for each reception depth, frequency values as upper limits of frequency bands in a plurality of reception depths; a frequency band setting unit configured to set a frequency band of the frequency spectrum in the specified reception depth, calculated by the frequency analyzer, based on a frequency value in the specified reception depth among the frequency values stored in the frequency band information storage unit; a reference spectrum information storage unit that stores, for each reception depth, reference spectra in the plurality of reception depths obtained based on frequencies of ultrasonic waves received from a reference reflector; a corrected frequency spectrum calculator configured to calculate a corrected frequency spectrum by correcting the frequency spectrum calculated by the frequency analyzer based on the reference spectrum in the specified reception depth among the reference spectra stored in the reference spectrum information storage unit; and a feature data extracting unit including an approximating unit configured to perform an approximating process only on a part of the corrected frequency spectrum calculated by the corrected frequency spectrum calculator, the part of the corrected frequency spectrum being included in the frequency band set by the frequency band setting unit, the feature data extracting unit being configured to extract feature data indicating the tissue property of the subject using a result of the approximating process performed by the approximating unit; wherein the frequency band setting unit is configured to set the frequency band which is used when the approximating unit performs the approximating process.