An underwater pump is provided to improve lubricating performance and water cooling effect by making a water screen between the rotor holder and the rotor. An underwater pump(1) comprises a motor unit(1-2) rotating a rotor(50) to generate power, and a pump unit(1-1) which inhales and discharges external water by rotating an impeller with the generated power. The rotor is installed inside a rotor holder(40). The impeller is installed inside an impeller housing(3). The impeller housing and a rotor housing(4) are formed on both sides of a partition wall. The water flowing in and out of the pump unit by the motor unit is guided into the motor unit through a circulation unit to form a water screen between the rotor holder and the rotor.
