An object information acquisition apparatus includes a holding member including a movable holding member configured to be movable in a direction of sandwiching an object, an irradiation member configured to irradiate the object with light from a light source through the holding member, an acoustic wave detection unit configured to receive an acoustic wave generated in the object by the light and to convert the acoustic wave into an electrical signal, a processing unit configured to acquire information in the object by using the electrical signal, a light diffusion member configured to be arranged on the movable holding member, and an imaging unit configured to capture an optical pattern formed when the light diffusion member is irradiated with the light, wherein the imaging unit is configured to be capable of adjusting a focus according to a movement of the movable holding member.
