A used photoacoustic apparatus includes: a light source capable of individually emitting light having a first wavelength at which absorption coefficients of oxyhemoglobin and deoxyhemoglobin are equal and light having a second wavelength an acoustic detector that receives acoustic waves generated when the light having the first and second wavelengths is absorbed by an object an absorption coefficient distribution generator that determines absorption coefficient distributions of an object interior a blood vessel position determining unit that determines a blood vessel position from an absorption coefficient distribution corresponding to the first wavelength an organism characteristics distribution calculator that determines an organism characteristics distribution from the absorption coefficient distributions and a trimming unit that trims the organism characteristics distribution in accordance with the blood vessel position.
