PURPOSE: To prepare a bun having extremely low smell and stringiness of NATTO (fermented soybean), very delicious taste and high nutritive value, by adding a sweetener to NATTO and using the obtained NATTO jam as the stuffing of a bun.

CONSTITUTION: NATTO jam is prepared by adding a sweetener, soy, wine, etc., to NATTO which may be finely cut or ground. The jam is wrapped with pastry composed mainly of wheat flour and the produced raw bun is steamed with a steamer at about 100°C for about 30min to obtain the objective bun stuffed with NATTO. The bun is cooled, packaged with a plastic film, sealed by heat-sealing and optionally frozen.