To provide a small-diameter hollow fiber membrane contactor capable of sealing a unit and a housing without using an O ring and a gasket.

The hollow fiber contactor 10 has a cartridge 24, shell 22, first end cap 26 and second end cap 28, wherein the cartridge 24 has a central tube 12 with holes of a sewing machine, hollow fiber cloth 16, first tube sheet 18, second tube sheet 20 and plug 15. The first tube sheet 18 and the second tube sheet 20 fix the above cloth at each end of the central tube 12, wherein a plug 15 is positioned in the first tube sheet 18. A hollow part of the hollow fiber 16 goes through to be opened in the first tube sheet 18 and is sealed at the second tube sheet 20. The shell, end caps, central tube, tube sheet and plug are made of the same material and are sealed by a material injecting from outside.