A pump includes: a pump chamber for which a capacity is changeable; an inlet channel which allows a working fluid to flow into the pump chamber; an inlet side fluid resistance element disposed between the pump chamber and the inlet channel; an outlet channel which allows the working fluid to flow out of the pump chamber; and a pipeline element formed inside the outlet channel, wherein a rotational flow generation structure, which generates a rotational flow of the working fluid, is provided in the pump chamber, and wherein the outlet channel is located adjacent to the rotational center of the rotational flow.