a pair of head block 3 to circulate gas in hollow fiber membrane module 2 in which each head block has different humidity and said hollow membrane module 2 is comprised of multiple bunches of hollow fiber membrane 4 and a cylindrical housing 5 to fill a bunch of these hollow fiber membrane 4 a plurality of hollow fiber membrane 4 extends from one side end to the other respectively along an axial direction of housing 5 both end of peripheral portion is tightly stuck in the inner face of both end of cylindrical housing 5 under the condition of being banded by a potting with resin a plurality of peripheral aperture 6 to pierce between inside and outside of housing 5 is circumfentially formed at interval on both ends of peripheral housing 5 of each hollow fiber membrane module 2 a pair of said head block 3 is separated into a plurality of plate respectively to improve the manufacture ability and the construction regarding to the embodiment a pair of said head block 3 is separated into three plates of inside plate 7 intermediate plate 8 and outside plate 9 respectively and is comprised of sequentially polymerizing these ones a shaft hole 11 12 to insert and to support the end portion of said hollow fiber membrane module 2 is formed in said inside plate 7 and intermediate plate 8 a fit shaft portion with facet joint 14 fitting into a fit hole portion with facet joint 13 formed on the head portion in inserting direction of a shaft hole 12 of said intermediate plate 8 is.