Sweet noodle sauce also known as sweet bean sauce or sweet soybean paste is a thick, dark brown- or black-colored sauce is made from wheat flour, sugar, salt, ''mantou'', and ground yellow soybeans .
There are many different types of sweet noodle sauces depending on the different compositions and the different method of production, and each variation represents the unique local style of a particular region, and even within the same geographical region, different manufacturers produces different kinds of sweet noodle sauce. For example, in northern China, the use of sugar is far less than in southern China in term of amount added, while the usage of ''mantou'' flour as the main ingredient is a much more common practice. Traditionally, in these regions, a good brand of sweet noodle sauce is considered top quality when its sweet taste results not from the addition of sugar, but as a direct result of the fermentation of the starches contained in the sauce's ingredients.
Similar to the better known hoisin sauce, sweet noodle sauce is sometimes used in dishes such as Peking Duck and as a replacement for yellow soybean paste in ''zhajiang mian''; in Beijing cuisine, yellow soybean paste is the traditional accompaniment for these two dishes. Sweet noodle sauce is sweeter than yellow soybean paste, which is saltier.
Sweet noodle sauce can be found in a typical Asian supermarkets under various English names, but with a common Chinese name.
Sweet noodle sauce's Korean equivalent is the ''chunjang'' used in the dish ''jajangmyeon'' .