PURPOSE: To improve the sepn. performance of a titled module by opening one end of a fine porous glass tube bundle through a partition wall and sealing the other end respectively independently.

CONSTITUTION: When a gaseous raw material is supplied through an introducing pipe 3, the material flows among fine porous glass tubes 1 in parallel along the tubes 1 and is discharged from a discharging pipe 5. If the gaseous raw material is, for example, a water gas, gaseous H2 enters the inside of the tubes 1 more than gaseous CO, and the permeated gas contg. much gaseous H2 component flows from the right to the left in the tubes 1. Thus the gaseous raw material and the permeated gaseous flow approximately parallel in the forward end part (right end part) of the module as well and the gas separating performance is consequently improved.