The present invention relates to a UV fluid sterilizer, which is suitably formed to sterilize fluid having poor UV transmission. According to the present invention, the UV fluid sterilizer includes a plurality of UV sterilization units. The UV sterilization units include: small quartz tubes; inside UV lamps mounted in the small quartz tubes for radiating UV rays at the inside of fluid; large quartz tubes concentrically mounted outside the small quartz tubes for forming the flow spaces of the fluid; spring type coils spirally fixed to the outer diameter surfaces of the small quartz tubes for applying rotation force to the fluid; and UV transmission shrinks films for fixing the spring type coils to the outer diameter surfaces of the small quartz tubes in close contact and preventing foreign substances from being trapped in the flow spaces of the fluid, and are characterized in that a plurality of outside UV lamps are provided outside the large quartz tubes for radiating UV rays to the fluid, which flows through the UV sterilization units, from the outside.