We have investigated the effect of roasted burdock powder on the chronic constipation. This is a placebo-controlled prospective randomized crossover study. Ten subjects with chronic constipation took 2 kinds of supplementary diets for 2 weeks each. Control was simple freeze-dried miso soup and the experimental diet was that supplemented with 10 g of burdock powder. They reported their daily bowel habit. Bowel movement was also evaluated by radiopaque markers method. Seven cases completed the study. There were no significant differences in bowel frequency and stool consistency between two kinds of dietary supplementation, though burdock powder showed a tendency to increase bowel frequency and make stools softer. No adverse event was observed. Our preliminary results guarantee that the effects of burdock powder on the bowel habit should be re-examined in a larger study in future.