Disclosed are: a powder which exhibits good adhesion to the skin and has excellent dispersibility in an oil component or water； and a long-lasting cosmetic preparation which glides excellently smoothly during application and forms an excellently uniform cosmetic film.Specifically disclosed are: a flat cellulose powder processed with an amphiphilic substance, which is obtained by mechanically pulverizing a cellulose-based substance and one or more amphiphilic substances that are selected from the group consisting of phospholipids, ceramides, cholesterol and derivatives thereof, and phytosterols and derivative thereof； and a cosmetic preparation which contains the powder.
