A processing apparatus having a processor acquiring image data indicating oxygen saturation distribution inside an object by using signals derived from acoustic waves generated from a plurality of wavelengths of light. The processor acquires an oxygen saturation at a first position of a blood vessel of the object, generated by image reconstruction using signals, acquires a first correction amount to correct the oxygen saturation at the first position of the blood vessel, and acquires a second correction amount to correct the oxygen saturation in a second position of the object other than the first position, based on the first correction amount.
