Vertical shaft centrifugal pump, rotor for the pump, and air conditioner

In a conventional water discharge pump assembled in an air conditioner, the rotation of a blade wheel produces cavitation to cause a problem with quietness. A vertical shaft water discharge pump of the invention has a rotor (23), a casing (20), a cover (22) that forms, together with the casing (20), a pump chamber (21) in which the rotor (23) is received, a suction pipe (25) forming a suction path (24) communicating with a lower end central portion of the pump chamber (21), and a discharge port (26) communicating with the pump chamber (21). The rotor (23) has a rotor shaft (40) connected at its upper end section to a drive motor (16), a circular main plate (42) cocentrically integrally connected to the rotor shaft (40), pins (43) projecting from the main plate (42) substantially in parallel to the axis of the rotor shaft (40), and uniformly pressing sections (44, 46) formed in the main plate (42) and communicating between the front surface side and the back surface side of the main plate (42).