A lock comprises a lock casing, a shackle, an indicating device and a button component. The shackle is movably disposed on the lock casing. The indicating device is disposed in the lock casing, and moves from one original position to an indicating position with respect to the lock casing. The button component connects to the indicating device for restricting the movement of the shackle, the button component moves from a first position to a second position, for enabling the indicating device to move from the indicating position back to the original position.