ABSTRACT Arrowroot tuber has a potential to be developed as a functional food. Products processed from tubers of arrowroot such as flour and starch are more efficient in storage and have been known empirically for its antiulcer activity. This study aimed to analyse glucomannan and antiulcer activity of arrowroot tubers. Glucomannan was analysed using thin layer chromatography densitometry method. Antiulcer activity was determined by the administration of arrowroot flour tubers (AF), arrowroot starch tubers (AS), NaCMC (NC), Sucralfate (SC), and glucomannan (GC) to rats. The doses of flour and starch of arrowroot tubers were obtained from the conversion of the doses of fresh arrowroot tubers utilization in the community. Antiulcer activity was carried out by inducing rats with doses of asetosal 450 mg/kgbw for 10 days, then flour and starch of arrowroot tuber were administered orally for 5 days. On the 11th day, rats were sacrificed and the stomach was taken to analyse the destruction histologically. The result showed that glucomannan concentration of arrowroot tubers was 14,27 mg/g. There was no significant difference (p> 0.05) of the ulcer index between AF and AS compared to the normal control, so that it has the ability to heal ulcers caused by asetosal. The experimental findings suggest that arrowroot tuber can be useful for treating peptic ulcers. Keywords: arrowroot tubers, flour, starch, glucomannan, ulcers