A pump housing having a suction chamber and a discharge chamber. A partition wall dividing the suction chamber and the discharge chamber, and having a communication hole formed at a center thereof for allowing the suction chamber to communicate with the discharge chamber. An impact body disposed toward a suction part so as to come into contact with fluid introduced into the suction chamber through the suction passage; and a gas discharge part disposed at an upper portion of a circumferential surface of the housing and communicating with an outside so that gas, separated from the fluid in contact with the impact body, is discharged. The suction part extends in one direction perpendicular to a virtual center line passing through the housing, and the impact body is disposed in a direction opposite to an extending direction of the suction part with respect to the virtual center line.