PURPOSE: To reduce the generation of noise by a method wherein a period and vibration during resonance are made irregular.

CONSTITUTION: Kidney ports 13 respectively communicated with a plurality of cylinders 12 bored in a cylinder block 11 are aligned at an unequal pitch along a periphery. A cycle of delivery through each cylinder 12 during one full rotation of the cylinder block 11 is rendered irregular and the generation of noise during resonance is reduced. Further, the cylinders 12 are arranged at an unequal pitch along a periphery and a relative position in a peripheral direction between the cylinder 12 and the kidney port 13 is changed classified by each cylinder 12. This constitution changes pressure change characteristics in the cylinder 12 at every cylinder 12 and brings respective cylinders 12 irregular in a delivery pressure therethrough during one full rotation of the cylinder block 11, whereby, coupled with irregularity in a period of delivery, the generation of noise during resonance is further reduced.