To provide a pump device configured such that the impeller can be prevented from being moved toward a case body by which a pump chamber is defined. An impeller is arranged in a pump chamber defined by a case body and an end wall portion of a motor. The impeller includes back blades protruding from a shroud toward the end wall portion of the motor. When the impeller is driven to circulate fluid through the pump chamber, a fluid is drawn out by the back blades from a clearance between the impeller and the end wall portion of the motor. Therefore, the impeller is moved by the negative pressure toward the end wall portion of the motor. The back blades function as a suction power generation mechanism configured to generate suction power sucking the impeller toward the end wall portion.