The present invention has objects to provide an extract powder of indigo plant, which has a relatively low hygroscopicity, satisfactory fluidability, and improved storage stability； a process thereof； and a composition incorporated with the extract powder. The objects are solved by a process for producing an extract powder of indigo plant, which comprises incorporating a partial starch hydrolyzate with a dextrose equivalent of 10.2 or lower into one part by weight, on a dry solid basis, of an indigo plant extract contained in a liquid extract of indigo plant in an amount of not lower than 0.25 part by weight but not higher than 5 parts by weight, on a dry solid basis, and drying the resulting mixture； an extract powder of indigo plant prepared thereby； and a composition incorporated with the extract powder.
