Provided are a solid preparation that can easily regulate the dissolvability of medication, and a method to improve the dissolvability of medication. The disclosed solid preparation (1) is provided with a medication-containing part (2) that contains medication, a gel-forming layer (4) that coats the medication-containing part (2) and forms a gel by absorbing water, and, if necessary, an intermediate layer (3) interposed between the medication-containing part (2) and the gel-forming layer (4). By including a foaming agent (such as sodium bicarbonate) in the medication-containing part (2) and/or the intermediate layer (3), the dissolvability of the medication is improved. The medication-containing part (2) can contain cationic or basic medication, and the gel-forming layer (4) can contain an anionic or acidic polymer. The gel-forming layer (4) can be coated by a surface layer (adhesion prevention layer) (5).
