A built-in type electric driving system of a machine tool, comprising: a housing ; a hollow tube-shaped spindle extending from the housing in forward and backward directions and rotatably installed on the basis of the housing ; a built-in motor consisting of a stator fixed to the inside of the housing and a rotor fixed to an outer surface of the spindle , and configured to generate torque between the stator and the rotor by power applied from the outside to cause rotation of the rotor ; a chuck installed at a front end of the spindle and including a jaw configured to grip a workpiece; a drawbar installed at an inner side of the spindle to be linearly movable in the forward and backward directions, and having a front end connected to the jaw ; a drawbar key and a drawbar key groove configured to connect the drawbar to the chuck so that the drawbar is linearly movable, but not rotatable; a lead screw formed with a thread in a spiral shape on an outer surface thereof, and formed to be fixed to the drawbar ; a driving unit fixed to the outer surface of the spindle to rotate together with the spindle ; a female screw cover coupled to the driving unit to rotate together with the driving unit, and having a thread formed on an inner circumferential surface thereof to be screw-coupled to the thread of the lead screw (4:); and characterised by a chuck locking unit configured to restrict or release the rotational movement of the chuck on the basis of the housing ; and a clutch unit installed to be movable in the forward and backward directions between a front portion of the spindle and a rear portion of the chuck to restrict the spindle relative to the chuck or separate the spindle so that the spindle is rotatable relative to the chuck . a housing ; a hollow tube-shaped spindle extending from the housing in forward and backward directions and rotatably installed on the basis of the housing ; a built-in motor consisting of a stator fixed to the inside of the housing and a rotor fixed to an outer surface of the spindle , and configured to generate torque between the stator and the rotor by power applied from the outside to cause rotation of the rotor ; a chuck installed at a front end of the spindle and including a jaw configured to grip a workpiece; a drawbar installed at an inner side of the spindle to be linearly movable in the forward and backward directions, and having a front end connected to the jaw ; a drawbar key and a drawbar key groove configured to connect the drawbar to the chuck so that the drawbar is linearly movable, but not rotatable; a lead screw formed with a thread in a spiral shape on an outer surface thereof, and formed to be fixed to the drawbar ; a driving unit fixed to the outer surface of the spindle to rotate together with the spindle ; a female screw cover coupled to the driving unit to rotate together with the driving unit, and having a thread formed on an inner circumferential surface thereof to be screw-coupled to the thread of the lead screw (4:); and characterised by a chuck locking unit configured to restrict or release the rotational movement of the chuck on the basis of the housing ; and a clutch unit installed to be movable in the forward and backward directions between a front portion of the spindle and a rear portion of the chuck to restrict the spindle relative to the chuck or separate the spindle so that the spindle is rotatable relative to the chuck . a chuck locking unit configured to restrict or release the rotational movement of the chuck on the basis of the housing ; and a clutch unit installed to be movable in the forward and backward directions between a front portion of the spindle and a rear portion of the chuck to restrict the spindle relative to the chuck or separate the spindle so that the spindle is rotatable relative to the chuck . <EOS>