An image processing device includes a rotation processor, a parallax image generator, and a rotation controller. The rotation processor makes rotation processing including rotating first left and right images in a stereo image, to generate second left and right images. The parallax image generator calculates corresponding left and right image points in the second left and right images, to generate a parallax image. The rotation controller obtains a coordinate point to calculate an amount of angular change in a rotation angle in the rotation processing. The coordinate point indicates relation of a first positional difference in a horizontal direction and a second positional difference in a vertical direction, between first and second positions. The first and second positions are respective positions of the left and right image points in the second left and right images.