This invention concerns an apparatus and a method for producing carbonated water capable of obtaining high concentration carbonated water effectively. Carbon dioxide gas is passed through a first carbon dioxide gas dissolver composed of a membrane module to be dissolved in water and the carbonated water passing through the first carbon dioxide gas dissolver is passed through a static mixer, which is a second carbon dioxide gas dissolver. Consequently, a high concentration carbonated water can be obtained remarkably, effectively and easily with a simpler structure than conventionally.