A full-circumferential flow pump includes a motor having a stator, a shaft rotatably disposed in the stator, and a rotor mounted on the shaft for rotation relative to the stator, an outer frame barrel disposed around the stator, an outer cylindrical pump casing disposed around the outer frame barrel with an annular space defined therebetween, and a pump assembly mounted on an end of the shaft for pumping a fluid into the annular space or pumping a fluid introduced from the annular space. The full-circumferential flow pump further includes an inner casing provided in the outer cylindrical pump casing for accommodating the impeller and a resilient seal disposed between the outer cylindrical pump casing and the inner casing for preventing a pumped fluid in the outer cylindrical pump casing from leaking towards a suction side of the impeller.