Digestibility of mannooligosaccharides obtained from thermal hydrolysis of spent coffee grounds was examined by in vitro digestion method. Mannooligosaccharides were resistant to human salivary ␣-amylase, artificial gastric juice, porcine pancreatic enzymes and rat intestinal mucous enzymes. Fermentation products of mannooligosaccharides in human large intestine were estimated by in vitro fecal incubation method. Mannooligosaccharides were fermented by human fecal bacteria and the products of fermentation were short chain fatty acids. Acetic, propionic and n-butyric acids were the main short chain fatty acids as end fermentation products. These results suggest that mannooligosaccharides are indigestible saccharides and are converted to short chain fatty acids in human large intestine. The short chain fatty acids are thought to improve the large intestinal environment. Moreover, they are absorbed and utilized by the host as an energy source.