The present invention provides a technique for improving the sweetness of stevia extract. A composition having an excellent sweetness quality can be obtained by combining rebaudioside A, which is a main sweetness component of stevia extract, with mogroside V, which is a main sweetness component of siraitia grosvenorii extract, at a weight ratio of 95:5 to 60:40. By using the mixture described above as a sweetener, favorable sweetness can be imparted to various products, such as foods, medicines or quasi drugs.