A catchment header allowing a plurality of membrane modules to be connected thereto, having a tubular catchment part with a Young's modulus of 4.0 GPa or less for collecting and taking out filtrated liquid from the membrane modules, wherein at least a part of the tubular catchment part is covered with a reinforcement member with a Young's modulus of 4.0 to 250 GPa, the tubular catchment part of the catchment header is preferably formed of a synthetic resin, and the cross sectional area thereof perpendicular to the longitudinal direction of the tubular catchment part is preferably 4 to 36 cm.sup.2.