A solid preparation sufficiently masking the unpleasant taste of pioglitazone or a salt thereof; a solid preparation sufficiently masking the unpleasant taste of pioglitazone or a salt thereof and having superior properties of superior disintegration property in the oral cavity, appropriate preparation strength, long-term preservation stability and the like is provided. The present invention provides a solid preparation comprising particles comprising (i) core particles comprising an excipient, and (ii) pioglitazone or a salt thereof and an acid-soluble polymer both coating the core particles.