Foldable storage device and cart

A foldable storage device, comprising a front board unit, a rear board unit, two side board units and two bottom board units and having an unfolded state and a folded state;

• wherein each of the side board units comprises a first side board and a second side board, respectively, one side of the first side board and one side of the second side board being connected by a shaft, the other side of the first side board and one side of the front board unit being connected by a shaft, and the other side of the second side board and one side of the rear board unit being connected by a shaft;
• wherein each of the bottom board units comprises a triangular bottom board main board and two triangular bottom board sub-boards, respectively, the bottom board main board being provided with a first main board short side, a second main board short side and a main board long side, the bottom board sub-board being provided with a first sub-board short side, a second sub-board short side and a sub-board long side, the sub-board long sides of the two bottom board sub-boards being connected to the first main board short side and the second main board short side of the bottom board main board by shafts, respectively, the first sub-board short sides of the two bottom board sub-boards of one of the bottom board units being connected to the bottoms of the first side boards of the two side board units by shafts, respectively, the first sub-board short sides of the two bottom board sub-boards of the other of the bottom board units being connected to the bottoms of the second side boards of the two side board units by shafts, respectively, when the first side board and the second side board rotate relatively, the bottom board sub-board rotating synchronously with the first side board or the second side board relative to the bottom board main board, so that the storage device is capable of being switched in the state and the folded state.