The present invention provides a rotary blood pump with both an attractive magnetic axial bearing and a hydrodynamic bearing. 0 and 150 nm, and the molding has a curved surface having a radius of curvature of not less than 40 mm and protruding on the surface side or a flat surface in the transparent window. The narrowband signal frequencies are analyzed for peak amplitudes which are summed to derive maintenance merit values related to the arcing phenomena.