A skin color image gamut weight detecting method and a device thereof are provided. The method includes: receiving an image including first color components and second color components; obtaining a skin color region, a skin color category, and a first gamut; obtaining first color component values and first cardinal numbers according to the first color components; obtaining second color component values and a plurality of second cardinal numbers according to the second color components; obtaining a second gamut and a weight center according to the skin color category, the first cardinal numbers, the second cardinal numbers, the first color component values, and the second color component values; obtaining a first weight area and a second weight area according to the first gamut and the second gamut; and obtaining a skin color gamut weight map according to the weight center, the first weight area, and the second weight area.