To provide an apparatus for cooling stored water in a water tank in which an illuminating lamp, etc., is lightened, capable of rationally preventing deficiency of heat capacity and heat loss which are defects of Peltier element in order to realize cooling by Peltier effect.

This cooling apparatus is constituted so as to simultaneously operate a cooling mechanism A for cooling storage of water in a water tank and a ventilation mechanism B for carrying out ventilation of air in the upper part of the water tank. As a result, air in the upper part of the water tank heated by an illuminating lamp, etc., is discharged and the temperature of the air is maintained to outside air temperature and contact of cold with high temperature air is prevented even when cold is carried to the upper layer of air of the water tank by convection current caused by cooling of stored water to prevent the loss of the cold.