A display controller (20) includes an information acquisition unit configured to obtain input data of attentional resources of an occupant of a mobile object such as traveling time, occupant status information, driving environment information or display image history and a display-image generation unit configured to generate, in a mode determined based on the input data, a display image to be displayed by a display device (10) provided for the mobile object. The mobile object is for instance a vehicle comprising a head-up display.