An upper casing receives a rotor, which is rotated by a drive force of a motor. The upper casing includes a pump chamber, which receives the rotor, a planar surface portion, which is formed around an opening of the pump chamber, and a through hole. A lower casing includes a planar surface portion, which is formed around the opening of the pump chamber, and a through hole. The lower casing closes the opening of the pump chamber to form the pump chamber in cooperation with the upper casing. A resilient sheet is placed between the lower casing and a mount portion of the motor and includes a through hole. A screw is received through the through holes of the upper casing, the lower casing and the resilient sheet to securely connect the upper casing, the lower casing and the resilient sheet to the mount portion. A lower casing side surface of the resilient sheet includes a plurality of primary protrusions.