Abstract: A canned motor pump having an enclosing casing on the inside of a stator and a rotor on the inside of the enclosing casing, in which the interior parts of the enclosing casing communicates with the interior parts of a pump. Surfaces of supported portions on a shaft of the rotor which are contacted with the liquid flowing on the inside of the enclosing casing are treated by electrolytic polishing so that a liquid liable to polymerization or an adherent liquid can normally circulate as a circulating liquid for cooling a motor, and furthermore supporting portions which support the shaft contain bearings produced from fluororesin or glass-fiber reinforced fluororesin.