A torque wrench includes a handle, a wrench, a clutch, an adjustor, a grip, a scale ring and a locking collar. The wrench includes a lever inserted in and pivotally connected to the handle. The clutch is connected to the lever to stop rotating a workpiece when a maximum value of torque is reached. The adjustor is connected to the clutch and includes a knob operable to adjust the maximum value of torque. The knob is provided with a first color. The grip is connected to the handle. The scale ring is connected to the grip. The locking collar is provided with a second color. The locking collar is movable between a locking position to prevent the knob from rotation relative to the grip and show the first color and an unlocking position to allow the knob to rotate relative to the grip and show the second color.