a humidifying module configured to humidify dry gas supplied from outside using wet gas discharged from a fuel cell stack;

a first cap coupled to one end of the humidifying module; and

a second cap coupled to the other end of the humidifying module, wherein

the humidifying module comprises: a mid-case having an inlet configured to allow wet gas to be introduced therethrough and an outlet configured to allow the wet gas to be discharged therethrough; and a cartridge disposed in the mid-case, the cartridge having a plurality of hollow fiber membranes coupled thereto,

the mid-case comprises a blocking member protruding toward the cartridge between the inlet and the outlet, the blocking member being configured to contact the cartridge in order to block passage of wet gas, and

the cartridge comprises: an inner case configured to receive the hollow fiber membranes; and an interlocking member configured to connect the inner case to the blocking member such that the blocking member and the inner case are moved in an interlocked state depending on pressure of wet gas located between the mid-case and the inner case.