To provide a multistage motor pump capable of making a vertical multistage pump to a horizontal multistage pump, making the horizontal multistage pump to the vertical multistage pump only by exchanging one part, and reducing the installation cost as a whole.

The multistage motor pump is equipped with an outer cylinder 6 provided on the outside of a motor frame 2, a first pump part increasing a pressure of the treated liquid by at least one impeller 14, and a second pump part increasing a pressure of the treated liquid by at least one impeller 15. The suction direction of the impeller 14 of the first pump part and that of the impeller 15 are reversed each other. A delivery side casing 3 having a delivery nozzle 3a toward the perpendicular direction to an axis can be mounted on the one end of the outer cylinder 6. Both a first suction side casing 1 having a suction nozzle 1a toward the perpendicular direction to the axis and a second suction side casing 101 having a suction nozzle 101a toward the axial direction can be mounted on the other end of the outer cylinder 6.