A preparation which can improve the solubility of an NPYY5 receptor antagonist in water even when the NPYY5 receptor antagonist is contained in the preparation at a high content is provided. When an NPYY5 receptor antagonist carboxymethylethylcellulose and optionally an amorphousization inducing agent are contained in a solid preparation the dissolution profile of an NPYY5 receptor antagonist was improved.