PHOTOCATALYST REACTOR

PROBLEM TO BE SOLVED: To provide a photocatalyst reaction unit and a photocatalyst reactor with a high processing capacity on the basis of high light utilization efficiency.SOLUTION: A photocatalytic reaction unit includes: a light guide body, which is provided with a light guide body substrate, which has a vertical axis line, a peripheral surface around the vertical axis line, and two end surfaces that cross the vertical axis line; and a photocatalyst layer affixed to the peripheral surface or an intermediate layer provided on the peripheral surface of the light guide body substrate, the photocatalytic reaction unit also being provided with a light source disposed such that the light therefrom is incident into the light guide body substrate from at least one end surface of the light guide body substrate and also having the light guide body inserted into a fluid to be processed. The light guide body has a plurality of annular grooves or at least one spiral groove centering in the vertical axis line such that at least a part of the light incident from the end surface radiates to the photocatalyst layer side.