1. A color gamut data creating device comprising: a receiving unit configured to receive measurement points concerning a device, the measurement points being defined in a color space that is capable of representing hue by a hue angle, the hue angle being defined by an axis perpendicular to an achromatic axis that represents lightness; a locating unit configured to locate characteristic points based on the measurement points on a target plane that has a constant angle of the hue angle; an extracting unit configured to extract at least three vertices of a color gamut from among the characteristic points, the at least three vertices satisfying conditions that a first point, which is any one of the at least three vertices, is located within a reference distance from a second point adjacent to the first point from among the at least three vertices, and that all cross products have the same sign, each cross product being calculated between a vector defined by the first point to the second point and each of a plurality of vectors defined by the first point to each of the respective characteristic points located within the reference distance from the first point; and a data creating unit configured to create color gamut data indicative of the color gamut, the color gamut indicating a distribution range of the characteristic points based on the at least three vertices extracted by the extracting unit.