A fluid exchange membrane module includes a case including at least two pairs of fluid inlets and fluid outlets, and a fluid exchange membrane installed within the case and disposed so that a dry fluid flowing between one pair of a fluid inlet and a fluid outlet does not directly contact a high-humidity fluid flowing between another pair of a fluid inlet and a fluid outlet in the operating state of the module. The fluid inlet for the high-humidity fluid includes a diffuser. The fluid exchange membrane module may adiabatically expand a fluid flowing toward one side of a fluid exchange membrane and thus increase the relative humidity of the high-temperature and high-humidity fluid so as to maximize fluid transmission through the fluid exchange membrane, and may decrease the pressure of the fluid so as to uniform pressure distribution of a fluid flow.