A photoacoustic imaging system which includes a treatment tool for surgery, a probe unit having an electroacoustic transducer section, an image generation section which generates a three-dimensional photoacoustic image, an information obtaining section which obtains information representing mutual relative positions and orientations of the treatment tool and the probe unit in a space, an image processing section which superimposes a treatment tool display on the photoacoustic image based on the information, and a control section which controls these such that the photoacoustic image superimposed with the treatment tool display is displayed on a display section in real time. When assisting in surgery, the present invention allows the surgeon to recognize the positional relationship between a treatment tool and a blood vessel in an easier and accurate way.