HUMIDIFIER

A water recovery device that allows a first gas to flow inside hollow fiber membranes and a second gas to flow outside the hollow fiber membranes, and that exchanges moisture between the first gas and the second gas, includes a hollow fiber membrane bundle in which plural pieces of the hollow fiber membranes are bundled, a storage case housing the hollow fiber membrane bundle in its inside, and a housing having an introduction hole and a discharge hole of the first gas and an introduction hole and a discharge hole of the second gas, and housing the storage case in its inside. The hollow fiber membrane bundle includes a first gas bypass passage that penetrates through an internal part of the hollow fiber membrane bundle in an axial direction and that has a channel cross-sectional area larger than a channel cross-sectional area inside the hollow fiber membrane.