A touch panel device includes a display unit, a detector, and a controller. The display unit displays an image (nautical chart) on a display screen. The detector detects touches at two positions on the display screen and touched positions thereof. The controller displays a distance and azimuths between the touched positions, based on the two touched positions that are detected by the detector and either one of coordinates on the image corresponding to the touched positions and information associated with the coordinates (positional information).