An impeller 22 includes a rotating shaft 7 supported rotatably by an upper bearing 9 and a lower bearing 20 at upper and lower ends, a plurality of vanes 6, an arm 18 coupling an inner circumferential side of the vanes to the rotating shaft, an annular coupling portion 8 coupled to an outer circumferential side of each vane, and a driven magnet portion 12 placed in a lower portion of the annular coupling portion. A drive magnet portion 16 provided at a rotor 13 and a driven magnet portion 12 are opposed to each other with a bottom wall of the housing interposed therebetween, and rotation of the rotor is transmitted to the impeller through magnetic coupling. A blockade member 23 is placed below the vanes and blocks a space in a region spreading between the rotating shaft and the annular coupling portion while leaving an opening 14 at least around the rotating shaft. In a configuration in which the rotating shaft of the impeller is supported by the upper and lower bearings and a lower portion of each outer circumferential edge of the vanes is coupled to the annular coupling portion, the formation of a blood clot in the vicinity of the lower bearing can be suppressed.
