An image acquisition device according to the present disclosure includes a lighting system and an irradiation direction decision section. In a module, a subject and an imaging element are integrally formed. The lighting system sequentially irradiates the subject with illumination light in a plurality of different irradiation directions based on the subject such that the illumination light transmitted through the subject is incident on the imaging element. The module acquires a plurality of images according to the plurality of different irradiation directions. Before the plurality of images are acquired according to the plurality of different irradiation directions, the irradiation direction decision section decides the plurality of different irradiation directions based on a difference between a first preliminary image and a second preliminary image. The first preliminary image is acquired when the subject is irradiated with first illumination light in a first irradiation direction, and the second preliminary image is acquired when the subject is irradiated with second illumination light in a second irradiation direction.