PURPOSE: To prepare a pasty food composition at a low cost, by adding and mixing a mucous substance derived from NATTO (fermented soybean) to a base food composition composed of sugar, water, etc. and having a saccharinity of ≥10.

CONSTITUTION: A base food composition composed of water and sugar such as glucose, fructose, sucrose, etc. and having a sugar content of ≥10wt%, is mixed with a mucous substance derived from NATTO. The mucous substance is a stringy mucin-type substance produced by bacteria belonging to Bacillus genus, and capable of increasing the viscosity of a sugar solution when swollen or dissolved in water. A viscous pasty food composition having a viscosity increased with the mucous substance derived from NATTO can be prepared by this process at a low cost. The product may be fluid or have little or no fluidity.