PURPOSE: To keep the filter sanitary even when not in use by incorporating a bacteriostatic medium holding a bacteriostatic substance to suppress the propagation of microorganism into the microporous cylindrical filter placed in a passage formed between the fluid inlet and outlet in the container and used to filter a fluid.

CONSTITUTION: Raw water is injected from an inlet 11, introduced into a space 19 formed between the inner periphery of a container 10 and the outer periphery of a cylindrical filter 20 and passed through the filter 20 to filter off the contained fine solid and microorganism. The filtered water is passed through a spare filter 30 and discharged to the outside from an outlet 15. The filter 20 is formed by laminating a filter main body 23 on the outer periphery of the cylindrical core 22 having many through-holes 21 and forcing a cap 24 into the one end face of the core 22. In this case, the main body 23 is formed with fibrous activated carbon, and a bacteriostatic medium covered with a bacteriostatic substance suppressing the propagation of the microorganism is incorporated into the main body.