To provide a damping water circulating treatment apparatus for enhancing the transparency of damping water and sufficiently spreading ultraviolet rays from an ultraviolet lamp or the like to enhance sterilization effect, and a damping water circulating treatment method.

The damping water circulating treatment apparatus 1 is constituted so that a potential adsorption filter device 2 utilizing the adsorption action of zeta potential is provided on the way of a circulating passage for circulating damping water and an ultraviolet irradiator 3 for irradiating damping water with ultraviolet rays is provided to the rear stage of the potential adsorption filter device 2. Since the transparency of damping water can be enhanced by adsorbing the turbidity component of damping water by the potential adsorption filter device 2 to remove the same, ultraviolet rays emitted from the ultraviolet irradiator 3 of the rear stage are sufficiently spread to damping water to enhance sterilization effect due to ultraviolet rays.