The present invention addresses the problem of developing a technique for significantly suppressing the secondary fermentation of natto in a temperature range of no higher than room temperature (low-temperature range) and significantly prevents the quality deterioration of natto during storage and distribution. There is provided bacillus subtilis var. natto belonging to bacillus subtilis which has the following mycological properties: (1) when the bacillus subtilis var. natto is inoculated in a cooked soybean, etc., and the soy is kept at any temperature in a range of 37-53°C, the bacillus subtilis var. natto is favorably fermented, and natto having favorable flavor and stringiness can be produced (2) in a test for measuring the maximum width of a colony when the colony is inoculated in an agar medium (pH 7.0) containing 10% (w/v) phyton peptone and having any concentration of 3-4% (w/v), and is cultivated at a gas-phase temperature of 20°C for 48 hours, when the maximum width of the colony obtained by inoculating and cultivating K-2 strain (NITE BP-1577) is 2-4 mm, the maximum width of the colony obtained by inoculating and cultivating the bacillus subtilis var. natto is 1 mm or less and (3) the base sequence constituting 16SrDNA exhibits an identity of 99% or more with the base sequence described in SEQ ID NO: 1.
