To provide a blood treatment apparatus capable of omitting the pretreatment (heat shrinkage) of a hollow fiber membrane and having no danger of the leak caused by the crack of a fixing agent or the peel of the fixing agent from a housing.

In the blood treatment apparatus, a ring (4) is arranged to the inside end of the housing (5), hollow fiber membrane bundles (6) are arranged along the length direction of the housing (5) and the outer peripheral shapes of the hollow fiber membrane bundles (6) are regulated to fix the end parts of the hollow fiber member bundles (6) to the inner surface of the end part of the housing (5) by using a fixing material (3). Further, a port (1) having a blood outflow and inflow port (1A) is mounted on the end part of the housing (5), and the fixing material (3) is clamped and sealed by the port (1), the ring (4) and the housing (5) without being bonded to the ring (4) and the housing (5).