To efficiently reduce vibration caused by instantaneous flow change in delivery, and improve calmness and durability.

This rotary pump is provided with a rotor 5 having top parts 5a-5c slidable to get in contact with a trochoid curvature surface 6 formed in an inner circumferential surface of a housing l to rotate, plural actuation chambers 16a-16c formed between the trochoid curvature surface 6 and a rotor outer circumferential surface of which volume is continuously changed to increase or decrease as the rotor 5 is rotated, an intake port 18 formed to be opened in a range where the volume of the actuation chambers 16a-16c in the housing 1 is increased, and a delivery port 19 forged to be opened in a range where the volume of the actuation chambers 16a-16c in the housing 1 is reduced. A pulsating pressure reducing device such as an air chamber 21 is provided at a position facing a delivery range of the delivery port 19 of the actuation chambers 16a-16c.