An ultraviolet-and-ozone disinfection apparatus 200 providing an improvement on disinfection, includes a disinfection tank 202, a mercury UV lamp 210 enclosed by a quartz tube 208 for generating UV light with air trapped between them undergoing UV irradiation to generate ozone, an ozone transmitting tube 216, a spiral water transmitting tube 215 wrapping around the quartz tube in a spiral manner to achieve sufficient disinfection by mixing ozone in water, a sleeve barrel enclosing the spiral tube. Along the entire flow path, water is exposed to UV radiation to achieve sufficient disinfection and reduce excessive ozone that is harmful to human health.