A foldable enclosure structure containing a fabric cover defining a desired shape when expanded to an expanded position; a first supporting frame fixedly attached to the cover and a second supporting frame provided within the cover and rotatably coupled to the first frame such that the second frame is movable between a collapsed position and an expanded position. The second frame is superposed over the first frame in the collapsed position for ease of storage, but is rotated axially to intersect with the first frame in the expanded position to prop up the cover to the desired shape. To ensure that the structure is stable in the expanded position, fixing means is/are provided for fixedly attaching the second frame to the first frame in the expanded position.