A centrifugal fluid pump assembly (200) comprises a centrifugal fluid pump (205) and a control device (206). The centrifugal fluid pump (205) comprises a centrifugal fluid pump section including a housing and an impeller having a first magnetic material and a second magnetic material disposed thereof and accommodated for rotation in the housing and without contacting the housing, an impeller rotational torque generating section including a rotor having a magnet for attracting the first magnetic material and a motor for rotating the rotor, and an impeller position control section having an electromagnet for attracting the second magnetic material. The control device (206) includes a monitoring function of monitoring electric current flowing through the electromagnet; a monitoring function of monitoring motor-driving current; a monitoring function of monitoring the number of rotations of the motor; and a function of determining whether or not the impeller has a power swing by utilizing a current value monitored by the electric current monitoring function, a value of the motor-driving current monitored by the motor-driving current monitoring function, and the number of rotations of the motor monitored by the monitoring function of monitoring the number of rotations thereof.