PURPOSE: To prevent a driving device from being influnced by reactive force of the breakage of a wire saw even in case of occurrence thereof, by cutting a concrete structure always by stable force by means of the wire saw.

CONSTITUTION: An engine 5 is installed on a truck 14 equipped with wheels 2 and 3 which travel on a rail 1, and the output shaft 6 of the engine 5 and a pulley 7 for driving a wire saw 21 are connected to each other through a clutch 10. The output shaft 6 is connected to the wheels 2 and 3 through a hydraulic type speed change gear 11 for travelling speed adjustment 15 and a solenoid clutch 16 respectively. A concrete structure is cut always by stable force, and even in case of the breakage of the wire saw, a driving device is prevented from being influenced by the reactive force thereof.