PROBLEM TO BE SOLVED: To provide a hollow fiber membrane medical instrument which enables the effective prevention of the occurrence of dielectric breakdown in an electron beam sterilization treatment process.SOLUTION: The hollow fiber membrane medical instrument includes: a tubular container hollow fiber membranes headers provided with nozzles a port provided in the lateral surface of the tubular container and serving as an entrance of fluid nozzle caps detachable from the nozzles and a port cap 20 detachable from the port. There are provided a first space formed between the inside of the hollow fiber membranes and the inner surfaces of the headers and a second space formed between the outside of the hollow fiber membranes and the inner surface of the tubular container. The port cap 20 has, in a part of a top plate 20a at least, a low volume resistivity portion produced from a polymeric material having a volume resistivity of 5×10Ωcm or less, the portion being in contact with a space outside the hollow fiber membrane medical instrument on the outer surface side of the port cap 20 and being in contact with a second space of the hollow fiber membrane medical instrument on the inner surface side of the port cap without discontinuity. The hollow fiber membrane medical instrument is irradiated with an electron beam.
