To provide a gas dehumidifying membrane filter not using purge gas from outside of hollow fiber of a case for purging steam discharged to the fiber outer wall face in a water separating filter.

In the water separating hollow fibers 1, gas containing water sent from an inlet 6 of the hollow fibers 1 has lower pressure than the gas sent in, is dissipated to the atmosphere across a hollow wall membrane of the hollow fibers 1, and dehumidified gas is discharged from an outlet 7 of the hollow fibers 1. Spaces are provided to the hollow wall membrane allowing permeation of gas together with water, and the water having passed through the spaces is dissipated to the outside by the gas having passed through the spaces. The water separating filter 10 has one end of a fiber bundle formed by bundling a lot of the water separating hollow fibers 1 as the inlet 6 of water-containing gas, and the other end as the outlet 7 of the water-separated gas.