To provide a hemodialyzer reducing pain associated with hemodialysis, and safely usable even at home.

The hemodialyzer includes a needle 10 having a suction passage and a discharge passage separated from each other by a barrier film provided therein; a hemodialysis filter 30 for filtering and discharging the blood supplied; a tube 20 connecting the needle 10 to the filter 30 so that the blood can circulate; a drive part 40 producing a driving force to pass the blood through the filter 30; a sensor part 60 for detecting the speed of blood flow through the filter 30; and a control part 50 which stops the drive of the drive part 40 based on the detection by the sensor part 60.