[Object] An object of the present invention is to provide an oral solid preparation that can be produced in a simpler manner than conventional methods, that exhibits high bioavailability and high dissolubility even in persons having low stomach acid, and that can also ensure dissolubility after being allowed to stand for a certain period of time. Another object is to provide a simple method for producing the oral solid preparation.[Means for Achieving the Object] The present invention relates to an oral solid preparation comprising, as an active ingredient, a finely milled crystal obtained by milling an aripiprazole hydrate crystal, and a pharmaceutically acceptable carrier, the finely milled crystal having a mean particle size of 15 μm or less； an oral solid preparation comprising, as an active ingredient, a finely milled powder obtained by milling a highly hygroscopic aripiprazole anhydrous crystal, and a pharmaceutically acceptable carrier, the finely milled crystal having a mean particle size of 10 μm or less； a method for producing an oral solid preparation comprising the steps of (1) milling an aripiprazole hydrate crystal into a finely milled crystal having a mean particle size of 15 μm or less, and (2) mixing the obtained finely milled crystal with a pharmaceutically acceptable carrier； and a method for producing an oral solid preparation comprising the steps of: (1’) milling a highly hygroscopic aripiprazole anhydrous crystal into a finely milled powder having a mean particle size of 10 μm or less； and (2’) mixing the obtained finely milled powder with a pharmaceutically acceptable carrier.本發明之課題在於提供一種經口固態製劑，其能用比以往更簡易之方法製造，且即便對於低胃酸者亦具有高生物可用度及高溶出性，進一步，亦可確保放置一定期間後之溶出性，及製造該經口固態製劑的簡易製造方法。本發明係有關於：一種含有將作為有效成份之阿立哌唑之水合物結晶粉碎而成的微粉碎結晶、及藥學上容許之載體的經口固態製劑，其微粉碎結晶之平均粒徑為15μm以下；一種含有將作為有效成份之高吸濕性之阿立哌唑無水物結晶粉碎而成的微粉碎粉末、及藥學上容許之載體的經口固態製劑，其微粉碎粉末之平均粒徑為10μm以下；一種經口固態製劑之製造方法，包含(1)將阿立哌唑之水合物結晶粉碎，獲得平均粒徑為15μm以下之微粉碎結晶之步驟、(2)將獲得之微粉碎結晶與藥學上容許之載體混合之步驟；以及一種經口固態製劑之製造方法，包含(1')將高吸濕性之阿立哌唑無水物結晶粉碎，獲得平均
