A photoacoustic apparatus is used that has: a detecting unit that detects photoacoustic waves generated by an object containing contrast agent in first blood vessels of circulating blood and in second blood vessels； and a signal processing unit that generates contrast agent distribution and acquires contrast agent concentration change in the circulating blood. The signal processing unit acquires the position of the first blood vessels on the basis of a time-series change of the contrast agent distribution and the contrast agent concentration change, and lowers the concentration at the position of the first blood vessels on the basis of the contrast agent distribution.
