Oral preparation in which bitter taste of bitter-tasting drug is masked

Provided is a novel oral preparation (specifically, an intraoral quickly-disintegrating preparation) that allows a bitter-tasting drug such as silodosin, which has a very strong bitter taste, to be taken without an uncomfortable feeling and even without water, and that has solubility sufficient for reproducing a blood concentration effective for treating dysuria accompanying benign prostatic hyperplasia. The present invention pertains to masking particles and a novel oral preparation containing said masking particles. The masking particles are obtained by granulating or coating drug particles containing a bitter-tasting drug (e.g. silodosin) with a coating agent containing a methyl methacrylate-diethylaminoethyl methacrylate copolymer, wherein the content of said copolymer is 80-400 parts by mass relative to 100 parts by mass of the bitter-tasting drug (e.g. silodosin).