Abstract: A locking device for securing the coin box of coin operated vending and amusement machines is provided. An elongated flat locking bar is pivotally connected to the face of the coin operated machine by means of a spring loaded pivot pin for swinging movement parallel to said face between a locking position extending across and in close juxtaposition to the access door of the coin box and an open position permitting access to said door. A locking pin extends through an opening in the free end of the locking bar and a corresponding opening formed in the face of the machine to a point on the interior of said machine adjacent to the coin box. A barrel lock normally provided to lock the access door of the coin box is fitted with a lever having a retaining notch formed therein which is adapted to engage the inner end of the locking pin in its locked position. Access to the barrel lock from the exterior of the coin operated machine is obtained by a suitable opening formed in the locking bar.