An image processing device includes a first extracting unit, a second extracting unit, a face detecting unit, a first apex detecting unit, and a decider. The first extracting unit is configured to extract, based on distance information regarding an object, a first area representing the object. The second extracting unit is configured to extract contour directions of a contour of the first area. The face detecting unit is configured to detect a first face in the first area, based on the contour directions extracted by the second extracting unit. The first apex detecting unit is configured to detect a first apex indicating a boundary of the first face. The decider is configured to decide on a principal face of the object represented by the first area, based on at least the first face and the first apex.