Functional water (drinking water) having a dissolved oxygen content of 25 to 70 mg/l immediately after processing to dissolve oxygen in source water, and remaining 15 mg/l or more after the functional water is exposed to air for 24 hours. A purification processor (11) processes the source drinking water, and an additive processor (15) then adds components such as vitamins, minerals, and amino acids. An oxygenation processor (20) then produces the functional water (drinking water) by dissolving oxygen in the source water after having been processed by the additive processor (15). A bottling processor (16) then fills transportable containers with the drinking water and seals the containers.