PURPOSE: To secure the feed pump discharge performance by forming a communicating passage applying the feed pump discharge pressure to chambers formed with a rotor and vanes on either one of the rotor, a casing and a vane cover.

CONSTITUTION: Vane grooves 10 are formed at four positions at a uniform interval on the outer periphery of a rotor 9, vanes 11 are movably inserted in the radial direction of the rotor 9, and their tips are brought into contact with the inner periphery of a pump casing 6. A circular groove 21 is formed at the connection section between a casing 1 and the rotor 9 of a feed pump P, the circular groove 21 is communicated to a discharge port 17 via a communicating path 22, and it is communicated to the vane grooves 10. The fuel discharged by the feed pump P is guided into the vane grooves 10 via a discharge port 17, communicating path 22 and circular groove 21. The vanes 11 are excited outward by the fuel pressure, a gap is prevented from being generated between the tips of the vanes 11 and the inner periphery of the pump casing 6, and the efficiency of the feed pump P is improved.