A centrifugal blood pump apparatus includes an impeller (10) provided in a blood chamber (7), first and second permanent magnets (15, 17) provided in one surface and the other surface of the impeller (10) respectively, a third permanent magnet (16) provided in an inner wall of the blood chamber (7), and a magnetic element (18) and a coil (20) for driving the impeller (10) to rotate with a diaphragm (6) being interposed. First and second grooves for hydrodynamic bearing (23, 24) different in shape and depth from each other are formed in the inner wall of the blood chamber (7) facing the impeller, and third and fourth grooves for hydrodynamic bearing (21, 22) different in shape and depth from each other are formed in the diaphragm (6) facing the impeller (10). The second and fourth grooves for hydrodynamic bearing (24, 22) generate high hydrodynamic pressure when the impeller (10) is activated to rotate, while the first and third grooves for hydrodynamic bearing (23, 21) generate high hydrodynamic pressure when the impeller (10) steadily rotates.
