To combine advantages of both axial stream pump design and radial stream pump design by delimiting the surface of a conical trapezoid having a specific conical angle by a port structure which is directly adjacent to a recessed section in an end fringe part in the axial direction of a rotor.

A pump 10' includes a fixed and annular housing 20, and head part structures 30L and 30R are fixedly connected with a left end fringe part and a right end fringe part of the housing 20, respectively. Moreover, conical port members 40L and 40R are mounted on the head part structures 30L and 30R, respectively. Here, angles ALPHA of conical faces of the head part structures 30L and 30R are set to be larger than about 15 degrees and smaller than about 75 degrees to mix flow. A total length can be greatly shortened in accordance with a great increase of the conical angles. Moreover, this mixed flow liquid ring pump acts in such a manner that a large speed component in the axial direction is given to a fluid which flows between the circular cone and a rotor 70.