PROBLEM TO BE SOLVED: To provide a natto bacterium having a reduced spore-forming capacity, and also the natto having less spores to which disinfection and sterilization are hard to be performed.SOLUTION: This creation of a variant natto bacterial strain having the reduced spore-forming capacity by the destruction of spore-forming gene is provided, and the natto having less natto bacterial spores, produced by using such the natto bacterial strain is also provided.