An object of the present invention is to provide a coated solid preparation applicable to a one-dose pack, wherein, even when the preparation is in an unpacked state, the stability against moisture of valproic acid or a pharmacologically acceptable salt thereof contained therein is maintained and the deliquescence is suppressed. The present invention provides a coated solid preparation which contains as an active ingredient valproic acid or a pharmacologically acceptable salt thereof and is coated with a coating layer containing polyvinyl alcohol and swelling clay, wherein the mass ratio of the polyvinyl alcohol to the swelling clay is 8:2 to 3:7 and the swelling clay is dispersed as a laminated structure.
