Provided is a carbonated water mixing device. According to an illustrative embodiment of the present invention, the carbonated water mixing device comprises: a mixing unit which produces carbonated water by mixing raw-material water and carbon dioxide gas a storage tank which is linked to the mixing unit via a transfer line so as to store a set amount of the carbonated water produced in the mixing unit, and which discharges same to the outside via a discharge line and a pressurising unit which is provided on the transfer line so as to pressurise the carbonated water being transferred from the mixing unit to the storage tank side. Here, the storage tank is disposed such that the lower side thereof is immersed in cooling water stored in a cooling-water tank of a water-storing apparatus, and thus the carbonated water that has flowed to the storage tank side can be naturally cooled via the cooling water stored in the cooling-water tank.
