A photoacoustic imaging apparatus includes holding members configured to hold a subject, an acoustic wave conversion unit configured to receive an acoustic wave generated by irradiating the subject, which is held by the holding members, with light from a light source and convert the acoustic wave into an electric signal, a processing unit configured to generate image data from the electric signal, and an imaging unit configured to capture an optical pattern generated on a light diffusion member by emitting the light to the light diffusion member arranged on a surface of a side where the subject is irradiated with the light in the holding members where the holding members contact the subject in holding the subject, wherein the processing unit calculates light absorption coefficient distribution in the subject based on the optical pattern captured by the imaging unit and the electric signal acquired by the acoustic wave conversion unit.