An ultrasound observation apparatus of the present invention is an ultrasound observation apparatus capable of creating a blood flow image of a subject by receiving a reflection signal of a sound output signal transmitted to the subject as an electric signal, and performing various kinds of signal processing for the electric signal, and includes a transmission frequency switching section switching a frequency band of the sound output signal which is transmitted to the subject to a frequency band corresponding to an instruction signal which is outputted from an operation instructing section, and a blood flow color creating section changing a color at a time of visualizing the blood flow image by linking with switching of the frequency band by the transmission frequency switching section.
