A display device for a work machine includes a position information acquisition unit configured to acquire position information of a work machine, a peripheral information acquisition unit configured to acquire peripheral information indicating an existing structure, terrain, or a boundary of a zone around a position indicated by the position information of the work machine, an augmented image generation unit configured to generate an augmented image in which the existing structure, the terrain, or the boundary of a zone is viewed from a predetermined viewpoint of the work machine, and a display processing unit configured to display the augmented image of the existing structure, the terrain, or the boundary of a zone while superimposing the augmented image on a field of view from the predetermined viewpoint of the work machine or on an image of the field of view.