An apparatus was developed to measure mass transfer rate of a solute through a single hollow-fiber membrane fixed on the axis of a circular tube. Mass transfer rates of three solutes for four hemodialysis membranes were measured with the apparatus at a constant flow rate of a solution in the lumen and at various flow rates of pure water in the tube, The boundary mass transfer coefficient around a single hollow-fiber hemodialysis membrane measured with the apparatus was higher than that calculated with a theoretical equation. The discrepancy is considered to be caused by local convection flow that is unavoidable for a hollow-fiber membrane with flow in the lumen. Furthermore, diffusive solute permeability of a hollow-fiber membrane is obtainable with the apparatus.