To provide a humidifying membrane module that is reduced in weight, size and cost by making a case in a single layer structure, the humidifying membrane module has a hollow fiber membrane bundle constructed from plural hollow fiber membranes, a case accommodating the hollow fiber membrane bundle, a first flow passage extending through hollows of the hollow fiber membranes, and a second flow passage extending through the outer surface sides of the hollow fiber membranes, the membrane bundle and the case are simultaneously integrated at both ends of the membrane bundle by using potting members sealing gaps between the membrane bundle and the case, an inlet and an outlet constructing the first flow passage are formed at the both ends of the case respectively, and an entrance and an exit constructing the second flow passage are formed in side surfaces near the both ends of the case respectively.