1. An object detection device comprising: an imager carried on a movable body; a first calculator that calculates an observed value of an image displacement among a plurality of images captured by the imager at respective different timings; a first object detector that detects an object candidate and acquires information of the object candidate; a second calculator that calculates a theoretic value of the image displacement on the basis of the information of the object candidate; and a second object detector that compares the observed value of the image displacement and the theoretic value of the image displacement and determines whether the object candidate is an object on the basis of the comparison result, wherein the second calculator calculates the theoretic value of the image displacement corresponding to the object candidate, and the second calculator calculates the theoretic value of the image displacement of a point that is located at a distance equal to a distance between the object candidate and the movable body.