To ensure stable operation for a long period by arranging a surface profile shape part which is displaced from a straight line matched with the shape of the control rim of a reversing element at a horizontal cross sectional surface which is perpendicular to a turning axial line, in a turning contact range where the pressure surface of a vane is brought into contact with the control rim of a reversing member.

In a pump 20 in which four turning vanes 35 are arranged in a ring shaped passage 30 freely to turn, in an annular passage 30, its feed passage part 54 is formed on a horizontal cross sectional surface corresponding to the shape of a vane 70 arranged in a horizontal direction to a rotational direction. A reversing member 90.1 formed by a cylindrical rod which is bent about 90° is arranged on a part which is transferred from the feed passage part 54 to a seal passage part 55 due to turn a turning vane 35. A change member is arranged on a position which is symmetrically with the change member 90.1 in the range of a flow-in part 31, and an invasion member 91.2 is arranged on the change member to help turning of the vane 70 in the case where a pump is operated in a direction reverse to a rotary direction.