A foldable enclosure apparatus for a baby bed, characterized in that the foldable enclosure apparatus for a baby bed comprises: a hub device having four racks; a supporting assembly disposed around the hub device and having four side members deposited around the hub device; and four upper members being foldable, and each upper member having two ends and each end of the upper member pivotally mounted on two adjacent side members; and four linking devices respectively mounted on the side members of the supporting assembly, each linking device connected with the hub device and the upper member mounted on a corresponding one of the side members, and each linking device having a first linking assembly and two ends of the first linking assembly pivotally mounted on the hub device and the corresponding side member respectively, and the first linking assembly having a gear portion disposed at one of the ends of the first linking assembly connected to the hub device and engaging with one of the racks of the hub device; a rotating seat disposed at the other end of the first linking assembly connected to the side member and rotatably mounted to a bottom end of the side member; and a balance member mounted in the first linking assembly; and a second linking assembly mounted on the corresponding side member and having a bottom end fixed on the rotating seat; and a top end pivotally mounted on the two upper members mounted on the corresponding side member. a hub device having four racks; a supporting assembly disposed around the hub device and having four side members deposited around the hub device; and four upper members being foldable, and each upper member having two ends and each end of the upper member pivotally mounted on two adjacent side members; and four side members deposited around the hub device; and four upper members being foldable, and each upper member having two ends and each end of the upper member pivotally mounted on two adjacent side members; and two ends and each end of the upper member pivotally mounted on two adjacent side members; and four linking devices respectively mounted on the side members of the supporting assembly, each linking device connected with the hub device and the upper member mounted on a corresponding one of the side members, and each linking device having a first linking assembly and two ends of the first linking assembly pivotally mounted on the hub device and the corresponding side member respectively, and the first linking assembly having a gear portion disposed at one of the ends of the first linking assembly connected to the hub device and engaging with one of the racks of the hub device; a rotating seat disposed at the other end of the first linking assembly connected to the side member and rotatably mounted to a bottom end of the side member; and a balance member mounted in the first linking assembly; and a second linking assembly mounted on the corresponding side member and having a bottom end fixed on the rotating seat; and a top end pivotally mounted on the two upper members mounted on the corresponding side member. a first linking assembly and two ends of the first linking assembly pivotally mounted on the hub device and the corresponding side member respectively, and the first linking assembly having a gear portion disposed at one of the ends of the first linking assembly connected to the hub device and engaging with one of the racks of the hub device; a rotating seat disposed at the other end of the first linking assembly connected to the side member and rotatably mounted to a bottom end of the side member; and a balance member mounted in the first linking assembly; and a gear portion disposed at one of the ends of the first linking assembly connected to the hub device and engaging with one of the racks of the hub device; a rotating seat disposed at the other end of the first linking assembly connected to the side member and rotatably mounted to a bottom end of the side member; and a balance member mounted in the first linking assembly; and a second linking assembly mounted on the corresponding side member and having a bottom end fixed on the rotating seat; and a top end pivotally mounted on the two upper members mounted on the corresponding side member. a bottom end fixed on the rotating seat; and a top end pivotally mounted on the two upper members mounted on the corresponding side member.