NOVELTY - A motive power collection apparatus (10) comprises rotor by which flow path which opens between 1st wall orthogonal to rotation center and 2nd walls to radial direction is arranged radially, shaft which is arranged through rotation center of rotor, casing which stores rotor, forms 1st pressure chamber between said 1st walls, and forms 2nd pressure chamber between 2nd walls, 1st supply path (121) which supplies high pressure 1st liquid to flow path from rotation-center side of rotor, and 1st collection path (122) which collects 1st liquid from flow path.    USE - A motive power collection apparatus for sea water desalination apparatus (claimed).    ADVANTAGE - Energy loss is small by stabilizing rotation of rotor.    DETAILED DESCRIPTION - A motive power collection apparatus (10) comprises rotor by which flow path which opens between 1st wall orthogonal to rotation center and 2nd walls to radial direction is arranged radially, shaft which is arranged through rotation center of rotor, casing which stores rotor, forms 1st pressure chamber between said 1st walls, and forms 2nd pressure chamber between 2nd walls, 1st supply path (121) which supplies high pressure 1st liquid to flow path from rotation-center side of rotor, 1st collection path (122) which collects 1st liquid from flow path, 2nd supply path (131) which supplies low pressure 2nd liquid to flow path currently connected to 1st collection path from outer periphery of rotor, 2nd collection path (132) which collects 2nd liquids which pressure goes up from flow path currently connected to 1st supply path to outer peripheral side of rotor, and thrust shunt hole which connects 1st pressure chamber to 2nd pressure chamber. An INDEPENDENT CLAIM is included for a sea water desalination apparatus.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the sea water desalination apparatus with motive power collection apparatus.    Motive power collection apparatus (10)    1st supply path (121)    1st collection path (122)    2nd supply path (131)    2nd collection path (132)