To provide a water clarification apparatus capable of clarifying water quality by increasing an amount of dissolved oxygen in water in a water area regardless of the water depth of the water area.

The water clarification apparatus for clarifying the water quality in the water area A includes: a pressurizing part 1 for pumping water sucked up from the water area A; an oxygen injection part 2 for injecting oxygen into water; a pressure-dissolving part 3 for dissolving oxygen into water by pressurization of water injected with oxygen by being pumped by the pressurizing part 1; and a pressure reducing part 4 for reducing the pressure of oxygen-dissolved water dissolved with oxygen in the pressure-dissolving part 3 to the atmospheric pressure, sequentially toward a flow-out side from a flow-in side. The pressurizing part 1, oxygen injection part 2 and pressure-dissolving part 3 are continuously operated, so that the oxygen-dissolved water is continuously supplied to the pressure reducing part 4, and the oxygen-dissolved water without causing any bubbles is continuously discharged from a flow-out side of the pressure reducing part 4, then the treated water is returned to the water area A.