the present invention is made for supplying the humidifying module , which has a water permeable hollow fiber membrane bundle , at the about center part of which an bottomed inner flow passage are inserted , which gives the improved output responsibility and the startup responsibility , and which can prevent the occurrence of the remained water , even if the fluid containing steam and condensed water is led to the inner flow passage . for attaining these problems , there is provided a humidifying module comprising : a hollow fiber membrane bundle capable of performing a moisture exchanging between fluids streaming the inside and the outside thereof ; an inner flow passage inserted into said hollow fiber membrane bundle at the about central part with respect to the thickness direction of said hollow fiber membrane bundle so that the total insertion length thereof may be shorter than the length in the longitudinal directions of said hollow fiber membrane bundle , and said inner flow passage has inlet and outlet capable of passing said fluid , and has a bottom located near said outlet ; and a protrusion part disposed at said bottom so that it may be opposite to the flow direction of said fluid .