An input device includes a case body and a plurality of markers 30d, 30e, and 30p configured to emit light to the outside of the case body. When an angle difference between the normal directions of the two markers 30d and 30e is less than a predetermined threshold value, a distance between the two markers 30d and 30e is equal to or greater than a predetermined first distance. When an angle difference between the normal directions of the two markers 30d and 30p is equal to or greater than a predetermined threshold value, a distance between the two markers 30d and 30p is equal to or greater than a predetermined second distance, and the second distance is shorter than the first distance.