An inclination detecting device includes processing circuitry. The processing circuitry is configured to detect, in image information that is an image of an object imaged by an imaging device at an imaging position where a background member forms a background, a first boundary between the background member and a shadow of the object; detect a second boundary between the object and the shadow of the object in the image information; and detect an inclination of the object in the image information from the first boundary and the second boundary detected by the processing circuitry.