Novel non-reducing oligosaccharide having a structure represented by the formula of alpha-D-oligoglucosyl alpha-D-oligoglucoside is obtained by exposing either an aqueous solution which contains trehalose and an alpha-glucosyl saccharide or an aqueous solution which contains a non-reducing saccharide bearing a trehalose structure at its end to a saccharide-transferring enzyme. The oligosaccharide has a reduced sweetness, superior stability, appropriate viscosity and less or no susceptibility to crystallization or superior solubility when in crystalline form. These features make the oligosaccharide very useful in various compositions including foods, beverages, cosmetics, pharmaceuticals and shaped bodies.