PURPOSE: To intend easy movement of a carrier wheel and improvement of working efficiency by providing the carrier wheel on which a driving part of wire saw is loaded, at an operation floor of nuclear reactor building, so that a concrete wall of biological shield may be cut off and dismantled by a core boring machine and the like.

CONSTITUTION: First of all, a carrier wheel is placed at an operating floor of nuclear reactor building, and downward core boring is conducted from an upper edge of a concrete wall 44 of biological shield by a core boring machine, to circumferential direction of the wall, in sequence and at predetermined interval, with letting the carrier wheel move, and then cut-out cores are removed, and therewith bore holes 36 are drilled into the wall 44. After that, a wire saw 9 is driven with interval adjustment to interval between the holes 36 and 36, and the wall 44 between the holes 36 and 36 is vertically cut off. When the cutting is completed, a vertical rod 16 is lifted up, a table is turned around, and then a part of wall between the holes 36 and 36, and an inner or an inner or an outer side of the wall 44, is vertically cut off to direction of the wall thickness. Again, when the cutting is completed, the rod 16 is lifted up and the table is returned to the initial position, and then the wire saw 9 is made to go around in a loop going through from the holes 36 and 36, to the cut-off slit being cut in the previous turn, and the inner or the outer side of the wall 44, and finally the wall 44 is horizontally cut off to direction of the wall thickness.