Disclosed is a humidifier for a fuel cell having an improved humidification performance which can prevent a sudden decline of power at high speeds. The humidifier for the fuel cell of the present invention includes: a membrane housing having first and second end portions; a hollow fiber membrane bundle which is located within an inner space of the membrane housing and both ends of which are ported at the first and second end portions of the membrane housing, respectively; a humidity retainer which is located within the inner space of the membrane housing; a first cover unit which has an inlet for non-reactive gas of high humidity discharged from a stack and is mounted at the first end portion of the membrane housing; and a second cover unit which has an outlet for the non-reactive gas used for humidification and is mounted at the second end portion of the membrane housing.
