FUEL CELL MEMBRANE HUMIDIFIER

Disclosed is a fuel cell membrane humidifier which may prevent degradation of efficiency, which is caused by an increase in differential pressure in the fuel cell membrane humidifier due to volume minimization of the fuel cell membrane humidifier. A disclosed fuel cell membrane humidifier performs moisture exchange between a first fluid and a second fluid and includes a mid-case, a second fluid inlet configured to introduce the second fluid into the mid-case, a second fluid outlet configured to discharge the second fluid to outside, a partition wall partitioning an inner space of the mid-case into a first space and a second space, and an active bypass portion configured to adjust a flow rate of the second fluid flowing in the first space and the second space according to a flow rate of the second fluid introduced through the second fluid inlet.