Generally, a photoacoustic signal has a wavelength longer than a general ultrasonic signal. That is, it does not matter even if at the time of acquisition of the photoacoustic signal, an element pitch of a probe is several times as large as at the time of acquisition of the ultrasonic signal. Thus, at the time of acquisition of the photoacoustic signal, a plurality of neighboring elements in a receiving element array are collectively considered as one element, and a phasing process is performed. As a result, the same effect as a plurality of phasing addition circuits are disposed in parallel is obtained, and not only a phasing addition process of the photoacoustic signal but also image reconstruction can be performed in real time at a high speed.
