Abstract: Disclosed is an ultraviolet oxidation device for decompositing organic materials present in water in low energy consumption and low cost, an ultrapure water production device using the same, an ultraviolet oxidation method, and an ultrapure water production method. An ultraviolet oxidation device including: a flow tank 10; photocatalyst fibers 12; an ultraviolet radiating unit 14; and an ultraviolet radiating unit housing unit 16 which is arranged to occupy an entire cross-section of the flow tank intersecting with flowing direction of the water to be processed in the flow tank 10; wherein the ultraviolet radiating unit housing unit 16 is constructed such that the water to he processed flows toward the ultraviolet radiating unit 14 from an upstream side, and after flowing in the housing unit 16, the water to be processed flows out to a downstream side, and is formed of a material that allows the ultraviolet rays from the ultraviolet radiating unit 14 to radiate the photocatalyst fibers 12.

Abstract: Provided are a high-activity photocatalyst fiber and a production method thereof. The photocatalyst fiber is a silica-based composite oxide fiber including a composite oxide phase of an oxide phase (first phase) mainly including a silica component and a metal oxide phase (second phase) including a metal other than silica, in which the ratio of at least one or more metal elements present in a metal oxide constituting the metal oxide phase (second phase) increases gradiently toward the fiber surface, a metal constituting the metal oxide phase (second phase) is formed in the form of particles, mesopores having an average micropore diameter of 2 nm to 30 nm are formed between the particles from the fiber surface toward the inside of the fiber, and platinum (Pt) particles having an average particle diameter of 0.5 nm to 10 nm are supported inside the mesopores.