A foldable box comprising: a bottom part comprising a pair of bottom plates (1a, 1b) folded inward by one or more bottom folding means; a front part connected to a front side of the bottom part; a rear part connected to a rear side of the bottom part; a left part connected to a left side of the bottom part and including a pair of left plates (4a, 4b) to be folded inward by one or more left folding means; and a right part connected to a right side of the bottom part and including a pair of right plates (5a, 5b) to be folded inward by the one or more right folding means, wherein the left part comprises a pair of left auxiliary plates provided adjacent to be folded inward when the pair of the left plates are folded inward, wherein lower sides of the pair of left auxiliary plates are connected to left sides of the pair of the bottom plates by a left variable folding means, and left and right sides of the pair of left auxiliary plates are connected to the pair of left plates by a pair of left auxiliary folding means, wherein the right part comprises a pair of right auxiliary plates provided adjacent to be folded inward when the pair of right plates are folded inward, wherein lower sides of the pair of right auxiliary plates are connected to right sides of the pair of the bottom plates by a right variable folding means, and left and right sides of the pair of right auxiliary plates are connected to the pair of the right plates by a pair of right auxiliary folding means, and wherein the pair of the left auxiliary plates and the pair of the right auxiliary plates are folded inward by the left variable folding means, the right variable folding means, the pair of the left auxiliary folding means, and the pair of the right auxiliary folding means when the bottom part, the left part, and the right part are folded inward, wherein the left auxiliary plates and the right auxiliary plates are made of a synthetic resin or made of a hard material. a bottom part comprising a pair of bottom plates (1a, 1b) folded inward by one or more bottom folding means; a front part connected to a front side of the bottom part; a rear part connected to a rear side of the bottom part; a left part connected to a left side of the bottom part and including a pair of left plates (4a, 4b) to be folded inward by one or more left folding means; and a right part connected to a right side of the bottom part and including a pair of right plates (5a, 5b) to be folded inward by the one or more right folding means, wherein the left part comprises a pair of left auxiliary plates provided adjacent to be folded inward when the pair of the left plates are folded inward, wherein lower sides of the pair of left auxiliary plates are connected to left sides of the pair of the bottom plates by a left variable folding means, and left and right sides of the pair of left auxiliary plates are connected to the pair of left plates by a pair of left auxiliary folding means, wherein the right part comprises a pair of right auxiliary plates provided adjacent to be folded inward when the pair of right plates are folded inward, wherein lower sides of the pair of right auxiliary plates are connected to right sides of the pair of the bottom plates by a right variable folding means, and left and right sides of the pair of right auxiliary plates are connected to the pair of the right plates by a pair of right auxiliary folding means, and wherein the pair of the left auxiliary plates and the pair of the right auxiliary plates are folded inward by the left variable folding means, the right variable folding means, the pair of the left auxiliary folding means, and the pair of the right auxiliary folding means when the bottom part, the left part, and the right part are folded inward, wherein the left auxiliary plates and the right auxiliary plates are made of a synthetic resin or made of a hard material.