Even when electroacoustic conversion elements with high nonlinearity are employed, a nonlinear imaging is carried out with extracting more nonlinear components. An ultrasonic wave beam is transmitted twice from the transmitter to an identical position on the imaging target, and the signal processor performs computation on the reception signals obtained in every transmission performed twice, thereby extracting a nonlinear component included in the reception signals. In one transmission out of the transmission performed twice, the transmitter delivers the transmission signal to all of multiple electroacoustic conversion elements for driving the electroacoustic conversion elements, and in the other transmission, the transmission signal is delivered selectively only to a part of the multiple electroacoustic conversion elements for driving the electroacoustic conversion elements.