A photoacoustic apparatus comprising a processing unit configured to obtain first image data corresponding to a first wavelength, obtain second image data corresponding to a second wavelength different from the first wavelength, perform normalization processing on at least one of the first image data and the second image data so as to decrease a difference in an image characteristic between the first image data and the second image data, and obtain position shift information associated with irradiation timing of the light having the first and second wavelengths on the basis of the first and second image data at least one of which is subjected to the normalization processing.