1. A label-information processing device for a multi-viewpoint image including plural images obtained by photographing a specific subject from a respective plurality of adjacent viewpoints, the device assigning label information to a remarkable portion depicted in one or more of the images, the device comprising: a display unit for displaying, as a to-be-displayed image, a specific image out of the plural images, the specific image including a region depicting the remarkable portion; and a controller for assigning the label information to the remarkable portion depicted in the specific image the specific image being displayed on the display unit, wherein the controller has: a first function of acquiring coordinates, in a three-dimensional space, of the label information in a coordinate space, the coordinates being in the coordinate space used to express the subject in the three-dimensional space; a second function of displaying, on the display unit, as the to-be-displayed image, a different image having a viewpoint different from the viewpoint of the specific image the different image depicting a remarkable portion identical to the remarkable portion depicted by the specific image; a third function of transforming the coordinates, acquired by the first function, of the label information into coordinates, on a plane, at which the label information is assigned to each of the images, the images being displayed on the display unit by the second function, the images having the different viewpoints from each other; and a fourth function of assigning the label information to each of the images, having the different viewpoints from each other, at predetermined positions obtained from the coordinates transformed by the third function, wherein, when the to-be-displayed image includes the region depicting the remarkable portion and satisfies a condition that an image having a viewpoint adjacent to the viewpoint of the to-be-displayed image depicts no remarkable portion, the controller magnifies the region depicting the remarkable portion in the to-be-displayed image before displaying the to-be-displayed image.