PURPOSE: To provide an air separator whose height is restricted and which sufficiently copes with the request for miniaturization and which excels in general applicability by simple constitution.

CONSTITUTION: This air separator 100 arranged in a water distribution line and for removing air mixed in a liquid flowing in the water pipe consists of a body 10 formed cylindrically, a feeding pipe 20 communicating with one end side of the body 10 and for feeding the liquid into the body 10 from its tangential direction, a delivery pipe 30 communicating with the other end side of the body 10 and for delivering the liquid from the body 10, and a discharge pipe 40 arranged on the axial center inside the body 10 and the discharging the liquid in the axial center part.