PURPOSE: To enable the water level of a water pump to be set on a high position, and suppress air to make stagnantly in the water pump when cooling water is filled by forming, in a nearly elliptical shape, a discharging port which is provided in order to discharge cooling water into an engine side, and which is provided while communicating with a spiral chamber so as to be directed toward a long shaft in vertical direction.

CONSTITUTION: A water pump 6 which is installed on a cylinder block is provided with a pump case 8 and a pump cover 10, and a suction port 12 for cooling water, an impeller chamber 16, a spiral chamber 18 which is communicated with the impeller chamber 16, and a discharging port 20 for cooling water are provided in the pump case 8. In this case, the discharging port 20 is formed in a nearly elliptical shape while being directed toward a long shaft (Y) in vertical direction, namely, it is formed in a long hole shape in vertical direction by a discharging port forming wall part 36. A water level (L) is thus positioned on an upper side more than that of a prior art when cooling water is filled. In the pump case 8, an air ventilating hole 52 is formed on the upper part of the spiral chamber 18 so as to discharge air in the upper part of the spiral chamber 18 toward the discharging port 20 side.