Disclosed is an oral sustained-release preparation which contains at least one active ingredient selected from the group consisting of fasudil hydrochloride and a hydrate thereof, the preparation comprising at least one sustained-release coated particle comprising a core having a surface and a coating formed on the surface of the core, wherein the core contains the active ingredient and the coating comprises a coating base material and a specific insoluble auxiliary material, and wherein the preparation exhibits, with respect to the active ingredient, a specific dissolution rate, as measured by the dissolution test. By using the oral sustained-release preparation of the present invention, it becomes possible to surely control the release of fasudil hydrochloride from the preparation, so that the effect of the active ingredient is maintained for a long period of time. Therefore, the burden of the patient who has to take the preparation can be decreased and the compliance with respect to the administration of the preparation can be improved. Also disclosed is a method for evaluating an oral sustained-release preparation containing the active ingredient, wherein the evaluation is conducted with respect to the sustained-release ability of the active ingredient.
