A photoacoustic apparatus includes a light irradiation unit configured to irradiate an object with light； a receiving unit configured to convert a photoacoustic wave generated from the object irradiated with the light from the light irradiation unit into an electric signal； an optical coefficient acquiring unit configured to acquire optical coefficient information of the object； a sound speed acquiring unit configured to acquire sound speed information of the object by using the optical coefficient information acquired by the optical coefficient acquiring unit； and an object information acquiring unit configured to acquire object information by using the electric signal and the sound speed information.
