A sterilization device includes a shell, an ultraviolet ray lamp tube fixed with a lamp support on an upper end of the shell, an inner quartz tube around the lamp tube, an outer quartz tube around the inner quartz tube, a stainless steel tube around the outer quartz tube, an inner passage between the inner and the outer quartz tubes, an outer passage between the outer quartz tube and the stainless steel tube, and a guiding member on the lower end of the shell; the guiding member has guiding holes to guide water along a spiral path, and a water inlet on a lower portion thereof, which communicates with the guiding holes; a covering member is threadedly engaged with an outer side of the lower end of the shell; the water inlet of the guiding member extends through the covering member; the covering member has a water outlet hole.