To provide an automatic water blocking device simple and convenient in handling by solving the problem that a hose can not be attached to the faucet unless the automatic water blocking device is dismounted and a water stop valve of a three-way or four-way valve handle having an erected valve stem is provided in general, although a device adapted to a water faucet to which a valve stem is horizontally attached is devised as an automatic water supply blocking device for stopping water supply by turning the water stop valve itself instead of an automatic water supply blocking device attached to a discharge port of water line.

This water faucet automatic blocking device is composed of a disc-like upper face mounting member 1 put on an upper part of the valve handle A, a lower face mounting member 2, a pair of pipe mounting fittings 3 attached to a water pipe on the opposite side to the discharge port C, a plate-like pulley mounting plate 4 provided in an upper part of the pipe mounting fitting 3, a pair of guide pulleys 5 attached to both ends on an upper side of the pulley mounting plate 4, a float member 10 suspended at a tip of an opening thread 8 on one side by winding the thread around an outer peripheral channel 7 of the upper face mounting member in the direction of opening, a weight member 11 suspended at a tip of a blocking thread 9 on the other side by winding the thread in the direction of blocking, and a pair of direction conversion pulleys 6 attached to a lower part of the pipe mounting fitting 3.