To improve the reliability of examination such as blood transfusion examination by shortening a process treatment time of a washing process and reducing dispersion of washing effects, and further to reduce the power consumption of the centrifugation for washing cells and elongate the life in a cell-washing centrifuge for washing the biological cells such as blood cells.

The cell washing centrifuge 20 serially and successively carries out a washing cycle consisting of four steps of (1) a washing liquid-feeding step, (2) a centrifugation step, (3) a supernatant-discharging step and (4) a swinging step without stopping the rotation of a motor.