To provide a potable water storing tank for emergencies by which a constant amount of tap water is always reserved, a handle of an opening/closing cock is automatically moved to a closing position so that a water taking-out pipe may be closed in no time upon the occurrence of an earthquake without a need for manpower even if the water is taken out through the taking-out pipe, and the amount of the potable water in the tank body can be secured.

A water supply pipe 9 supplying the tap water into the tank body 1 and the water taking-out pipe 10 taking the reversed water in the tank body 1 to the outside at a lower position are fitted to the tank body 1 reserving the potable water. The opening/closing cock 14 opening and closing a middle part of the water taking-out pipe 10 by the 90-rotation of the handle 13 is mounted to the water taking-out pipe 10, and a water taking-out cock 15 is mounted to the taking-out end thereof. A pendulum-rocking-type weight hammer 16 is mounted to an outer part of the tank body 1 so that the weight hammer 16 may hit the handle 13 of the opening/closing cock 14 by a swing caused by the shake of the earthquake and that the handle 13 may be moved to the closing position.