The aim of this study was to evaluate the effects of 40% sucrose replacement with oligosaccharides (fructo- orisomalto-) in sponge cakes. The 18 female college students were divided into two groups; fructooligosaccharide sponge cake group (FOS) and isomaltooligosaccharide sponge cake group (IMOS). In each group, the subjects received 50 g/d of sponge cake which contained about 8 g oligosaccharides for 2 weeks. The results were as follows: (1) Frequency of stool evacuation tended to increase after 1 week and significantly increased after 2 weeks in both groups. (2) Shape and color of stool did not change in FOS group but the IMOS group showed significant improvement. (3) The stool amounts per defecation were not significantly different in both groups. (4) The time of defecation decreased 50% after 1 week in FOS group and tended to decrease gradually in IMOS group. (5) Consistency of stool was significantly decreased after 1 week in both groups and continuously decreased until 2 weeks. (6) Effort for evacuation and comfort feeling after evacuation were significantly improved only in IMOS group after 2 weeks. (7) Gastrointestinal complaints concerning diarrhea, abdominal pains, nausea, flatulence, loss of appetite and weight and bloating were apparent. The symptoms such as abdominal pains, flatulence, and bloating in FOS group lasted for 2 weeks. However, the complaints appeared only during two or three days in IMOS group. In conclusion, our results suggest that isomaltooligosaccharide was more effective than fructooligosaccharide for preventing constipation because isomaltooligosaccharide worked safely in gastrointestinal lumen.