An ultrasonic observation apparatus which sends an ultrasonic wave to a sample and receives the ultrasonic wave reflected by the sample, the apparatus comprising: a signal amplifier which amplifies a signal of the ultrasonic wave received from the sample with an amplification factor according to a receiving depth; a B-mode image data generator which generates B-mode image data in which the amplitude of the signal of the ultrasonic wave amplified by the signal amplifier is converted into brightness and displayed; an amplification corrector which performs amplification correction to make the amplification factor constant with respect to the signal of the ultrasonic wave amplified by the signal amplifier regardless of the receiving depth; a frequency analyzer which calculates a frequency spectrum by analyzing the frequency of the signal of the ultrasonic wave corrected by the amplification corrector; and a feature data extractor including: an approximation unit which performs an approximation process on the frequency spectrum calculated by the frequency analyzer, thereby to extract pre-correction feature data therefrom; and an attenuation corrector which performs an attenuation correction process on the pre-correction feature data extracted by the approximation unit, thereby to extract feature data; or an attenuation corrector which performs an attenuation correction process on the frequency spectrum calculated by the frequency analyzer; and an approximation unit which performs an approximation process on the frequency spectrum on which the attenuation correction process has been performed by the attenuation corrector, thereby to extract feature data; the ultrasonic observation apparatus further comprising a feature data image data generator which generates feature data image data to display visual information corresponding to the feature data extracted by the feature data extractor. a signal amplifier which amplifies a signal of the ultrasonic wave received from the sample with an amplification factor according to a receiving depth; a B-mode image data generator which generates B-mode image data in which the amplitude of the signal of the ultrasonic wave amplified by the signal amplifier is converted into brightness and displayed; an amplification corrector which performs amplification correction to make the amplification factor constant with respect to the signal of the ultrasonic wave amplified by the signal amplifier regardless of the receiving depth; a frequency analyzer which calculates a frequency spectrum by analyzing the frequency of the signal of the ultrasonic wave corrected by the amplification corrector; and a feature data extractor including: an approximation unit which performs an approximation process on the frequency spectrum calculated by the frequency analyzer, thereby to extract pre-correction feature data therefrom; and an attenuation corrector which performs an attenuation correction process on the pre-correction feature data extracted by the approximation unit, thereby to extract feature data; or an attenuation corrector which performs an attenuation correction process on the frequency spectrum calculated by the frequency analyzer; and an approximation unit which performs an approximation process on the frequency spectrum on which the attenuation correction process has been performed by the attenuation corrector, thereby to extract feature data; an approximation unit which performs an approximation process on the frequency spectrum calculated by the frequency analyzer, thereby to extract pre-correction feature data therefrom; and an attenuation corrector which performs an attenuation correction process on the pre-correction feature data extracted by the approximation unit, thereby to extract feature data; or an attenuation corrector which performs an attenuation correction process on the frequency spectrum calculated by the frequency analyzer; and an approximation unit which performs an approximation process on the frequency spectrum on which the attenuation correction process has been performed by the attenuation corrector, thereby to extract feature data; the ultrasonic observation apparatus further comprising a feature data image data generator which generates feature data image data to display visual information corresponding to the feature data extracted by the feature data extractor.