A wash water processing method and a wash water processing apparatus in a simple structure capable of effectively decomposing organic matters and killing bacteria contained in wash water, extending the life of a filter of a filtration apparatus and an ion-exchange resin and, furthermore, extending a bacteria-killing/washing interval of a washing processing part. In the wash water processing apparatus (11) and the washing method, a wash water accommodation part (12) into which processed water processed in a washing processing part (10) flows and a filtration mechanism part (14) are connected and the wash water accommodation part has connected in a circulatable manner thereto an inflow flow path and an outflow flow path of a sterilization and purification unit which organically couples respective functions of an ozone supply part which supplies ozone, an ultraviolet irradiation part which irradiates with ultraviolet rays, and a photocatalysis part which causes a photocatalyst to act.