A blood pump apparatus comprises a housing, a centrifugal pump section including an impeller and rotating inside the housing to feed a fluid by a centrifugal force, an impeller rotational torque generation section for attracting thereto said impeller and rotating said impeller; and a plurality of grooves for hydrodynamic bearing provided on an inner surface of said housing at a side of said impeller rotational torque generation section, each of the grooves for hydrodynamic bearing having a first side and a second side both extending from a periphery of said portion in which a groove for hydrodynamic bearing is formed toward a central side thereof and opposed to each other, a third side connecting one end of said first side and one end of said second side to each other, and a fourth side connecting said other end of said first side and said other end of said second side to each other; said first side and said second side are formed as a circular arc respectively in such a way that centers of said circular arcs are different from each other.