In an aspect of the invention, first and second images having parallax are acquired by an imaging unit (202) including a first imaging part (202A) and a second imaging part (202B), and an angle between an imaging direction of the imaging unit (202) and a normal direction of a flat surface of an object to be inspected having the flat surface is calculated on the basis of the acquired first and second images. The pan/tilt of the imaging unit (202) are controlled by a pan/tilt control unit (210), but images for inspection showing the object to be inspected are taken and acquired by the imaging unit in a case in which the calculated angle is controlled to an angle within an allowable angle range.