A signal generation unit 10 generates, and sends to a transmission circuit 12, a driving signal for forming a transmission pulse. A probe 14 is transmission controlled to transmit ultrasound at a transmission frequency which is set using, as a reference, a resonance frequency of a bubble administered into a living organism, and also at a transmission sound pressure which is set using an expansion ratio of the bubble as a reference. The signal generation unit 10 outputs a transmission pulse having a waveform corresponding to a center frequency of about 1.5 MHz and a transmission sound pressure of about 200 to 300 kPa. With this structure, it is possible to increase a harmonic component obtained from the bubble while suppressing a harmonic component obtained from real tissue, so that extremely high CTR can be obtained.
