A montelukast-containing coated solid preparation can be applied to one-dose package, wherein the humidity stability of montelukast or a pharmacologically acceptable salt thereof contained therein is maintained even when the preparation is unpacked. A coated solid preparation contains as an active ingredient montelukast or a pharmacologically acceptable salt thereof and is coated with a coating layer comprising polyvinyl alcohol and swelling clay, wherein the mass ratio of the above-described polyvinyl alcohol to the above-described swelling clay in the above-described coating layer is 8:2 to 3:7.
