A method for producing a koji of a hot pepper paste with reduced capsaicin and/or dihydrocapsaicin content through action of enzymes secreted from a koji fungus includes adding a koji fungus to starting material for preparation of koji of hot pepper paste, and adding a predetermined amount of hot peppers one or more times to the material during the cultivating step performed by enzymes secreted from the koji fungus. The method can reduce the hotness of a hot pepper paste, while maintaining the intrinsic colors of traditional hot pepper pastes. Accordingly, it is possible to prepare various hot pepper paste products satisfying customer's diverse needs.