1. An image processing device comprising: a first acquiring unit configured to acquire image data captured by an image capturing device, the image capturing device capturing a plurality of images corresponding to different viewpoints; a second acquiring unit configured to acquire rotation information representing a degree of rotation of a plurality of images in displaying the plurality of images of the captured image data or a degree of inclination of the image capturing device in capturing the plurality of images; a display unit configured to display the plurality of images of the captured image data in a side-by-side arrangement; and a determining unit configured to determine, on the basis of the rotation information, an orientation and an arrangement of the plurality of images in displaying the plurality of images of the captured image data in the side-by-side arrangement, wherein an arrangement of image capturing units agrees with the arrangement of captured images that are displayed.