The present invention has an object to provide a gel composition which has an excellent skin whitening effect and shows high storage stability even when ascorbic acid, a salt of ascorbic acid, an ascorbic acid derivative, and a salt of an ascorbic acid derivative is blended, and to provide a pack cosmetic using the gel composition. The gel composition, which comprises the following components (A)-(D): (A) a tamarind seed polysaccharide; (B) a polyhydric alcohol; (C) at least one or more of ascorbic acid, a salt of ascorbic acid, an ascorbic acid derivative, and a salt of an ascorbic acid derivative; and (D) water.