PURPOSE: To fulfill the same effect as multiple state pump with simple construction by providing first and second casings defined by a partition wall and a water path leading from the peripheral side of first casing to the central portion of second casing.

CONSTITUTION: A partition wall 10 is interposed between opposed surfaces of both casings 6a, 6b so that first and second vortex chambers 8a, 8b do not communicate directly to each other at the respective their central portions and peripheral sides. Also, a water path 11 leading from the peripheral side of said chamber 8a to the central portion of said chamber 8b is provided. Water sucked from an intake port 7 into said chamber 8a in the rotation of an impeller 1 is sent from the peripheral side through the water path 11 to the central portion in said chamber 8b so that pressure of water in said chamber 8b is increased and the water is discharged from the peripheral side through a discharge port 9.