An image processing device includes: an image receiving part configured to receive an image of a target workpiece on a surface of a conveying path captured by means of the imaging unit; a position acquiring part configured to acquire a position of the target workpiece in the captured image; a tilt acquiring part configured to acquire, by using the position of the target workpiece in the captured image acquired by means of the position acquiring part, a tilt angle of an imaging plane of the imaging unit relative to the surface of conveying path; and an outputting part configured to output assistant information used for assisting in the adjustment of the posture of the imaging unit by using the acquired tilt angle.