A membrane humidifier is provided for a fuel cell. The membrane humidifier of the present invention includes a hollow housing, a joint member, a plurality of internal partition modules, and a plurality of hollow fiber membrane bundles. The hollow housing has a humid air inlet formed at one end thereof and a humid air outlet formed at the other end thereof. The joint member is formed integrally with an inner circumferential surface of the hollow housing. The plurality of internal partition modules are coupled to the joint member and arranged adjacent to each other in the hollow housing, and have a plurality of humid air guiding apertures passing therethrough. The plurality of hollow fiber membrane bundles are disposed in the plurality of internal partition modules, respectively.
