To obtain a soy sauce containing buckwheat being a high nutritive food which has little demands other than for noodles, is used in place of or in addition to wheat which has a very large demand, although low in self- sufficiency because of low domestic production as one of the main stocks for soy sauce, to provide buckwheat with a stable and large demands.

This soy sauce uses heat-treated and powdered buckwheat at 30% or more on the starch-containing stocks. This invention is mostly characterized by use of buckwheat in place of or in addition to wheat (including wheat bran) as one of the main stocks for soy sauce. The buckwheat is not the commercial flour, but shall be heat-treated before milling. It is not necessary to remove the outer skin, and untritiously preferable to use whole-buckwheat.