Cartridge case and information recording medium

A cartridge case of an information recording medium includes a case main body where a guide part is disposed on an inner surface of a top plate, a tape reel that includes a hub in the shape of a bottomed-cylinder and is rotatably enclosed inside the case main body, and a locking member that is guided in a state where rotation is restricted by the guide part, is enclosed within the case main body so as to be capable of moving in a direction toward and away from a base plate of the hub, and restricts rotation of the tape reel. The guide part includes a cylindrical first convex part disposed on the inner surface and a plate-like second convex part disposed on the inner surface. The locking member includes a main part, a cylindrical third convex part that is disposed on the main part and engages the first convex part, and a plate-like fourth convex part that is disposed on the main part and contacts the second convex part to restrict rotation of the locking member.