A forming apparatus comprising: a pair of inner frames having plate-like shape and incorporated in an outer frame which is uprightly provided on a base board, so as to move only in a vertical direction; upper and lower horizontal roll chocks (10,20) and right and left side roll yokes (30,40), locked between the inner frames so as to be separatable from each other by mechanical structures: two position adjusting devices (7,8) for moving the upper and lower horizontal roll chocks (10,20) close to or apart from each other, which are provided on the outer frame or the base board; two position adjusting devices (32,42) for moving right and left side roll yokes (30,40) which are locked between the inner frames close to or apart from each other, one of the two position adjusting devices (32,42) being installed at end portion between the inner frames, and the other being installed on the outer frame or between the inner frames so as to move in the vertical direction; and an exchanging rail provided in a lower part of the outer frame a horizontal direction perpendicular to a product proceeding direction, characterised in that the upper and lower horizontal roll chocks (10,20) are constrained from moving in the horizontal direction, and the right and left side roll yokes (30,40) are constrained from moving in the vertical direction, by the mechanical structures, when the inner frames ascend, thereby to lock the respective roll chocks (10,20) and yokes (30,40) at predetermined positions inside the inner frames, and the locks are released when the inner frames descend, so that a stack body of the roll chocks (10,20) and yokes (30,40) is formed, by mounting the right and left side roll yokes (30,40) on the lower horizontal roll chock, and mounting the upper horizontal roll chock on the right and left side roll yokes (30,40), thereby the stack body configured to be withdrawn in a direction of the rail. a pair of inner frames having plate-like shape and incorporated in an outer frame which is uprightly provided on a base board, so as to move only in a vertical direction; upper and lower horizontal roll chocks (10,20) and right and left side roll yokes (30,40), locked between the inner frames so as to be separatable from each other by mechanical structures: two position adjusting devices (7,8) for moving the upper and lower horizontal roll chocks (10,20) close to or apart from each other, which are provided on the outer frame or the base board; two position adjusting devices (32,42) for moving right and left side roll yokes (30,40) which are locked between the inner frames close to or apart from each other, one of the two position adjusting devices (32,42) being installed at end portion between the inner frames, and the other being installed on the outer frame or between the inner frames so as to move in the vertical direction; and an exchanging rail provided in a lower part of the outer frame a horizontal direction perpendicular to a product proceeding direction, characterised in that the upper and lower horizontal roll chocks (10,20) are constrained from moving in the horizontal direction, and the right and left side roll yokes (30,40) are constrained from moving in the vertical direction, by the mechanical structures, when the inner frames ascend, thereby to lock the respective roll chocks (10,20) and yokes (30,40) at predetermined positions inside the inner frames, and the locks are released when the inner frames descend, so that a stack body of the roll chocks (10,20) and yokes (30,40) is formed, by mounting the right and left side roll yokes (30,40) on the lower horizontal roll chock, and mounting the upper horizontal roll chock on the right and left side roll yokes (30,40), thereby the stack body configured to be withdrawn in a direction of the rail. two position adjusting devices (7,8) for moving the upper and lower horizontal roll chocks (10,20) close to or apart from each other, which are provided on the outer frame or the base board; two position adjusting devices (32,42) for moving right and left side roll yokes (30,40) which are locked between the inner frames close to or apart from each other, one of the two position adjusting devices (32,42) being installed at end portion between the inner frames, and the other being installed on the outer frame or between the inner frames so as to move in the vertical direction; and an exchanging rail provided in a lower part of the outer frame a horizontal direction perpendicular to a product proceeding direction, characterised in that the upper and lower horizontal roll chocks (10,20) are constrained from moving in the horizontal direction, and the right and left side roll yokes (30,40) are constrained from moving in the vertical direction, by the mechanical structures, when the inner frames ascend, thereby to lock the respective roll chocks (10,20) and yokes (30,40) at predetermined positions inside the inner frames, and the locks are released when the inner frames descend, so that a stack body of the roll chocks (10,20) and yokes (30,40) is formed, by mounting the right and left side roll yokes (30,40) on the lower horizontal roll chock, and mounting the upper horizontal roll chock on the right and left side roll yokes (30,40), thereby the stack body configured to be withdrawn in a direction of the rail.