THE PRESENT INVENTION PROVIDES A CONTROLLED RELEASE SOLID PREPARATION SUPERIOR IN THE STABILITY OF AN ACTIVE INGREDIENT, WHICH CAN EXHIBIT PHARMACOLOGICAL EFFECTS STEADILY AND RAPIDLY AFTER ADMINISTRATION, AND SHOWS A SUSTAINED PHARMACOLOGICAL EFFECT FOR A PROLONGED PERIOD OF TIME: A CONTROLLED RELEASE SOLID PREPARATION CONTAINING (1) AN ANTACID, (2) AN IMMEDIATE-RELEASE PART CONTAINING A COMPOUND UNSTABLE TO ACID AND A BASIC SUBSTANCE, AND (3) A SUSTAINED-RELEASE PART CONTAINING A COMPOUND UNSTABLE TO ACID AND A PH-INDEPENDENT MATERIAL IN COMBINATION.