PURPOSE: To drive liquid and generate motive force by deforming magnetic fluid contained in a cylindrical insulator into a spiral shape, and by rotating it around a cylindrical symmetry axis.

CONSTITUTION: When the switching section 32 of a switching means 31 is rotated, the connection between the switching section 32 and each switching contact 31a-31f is made in order, and a current flows into each exciting coil 25a-25f in order. On this occasion, each spiral magnetic pole 21a-21f with each exciting coil 25a-25f wound around is made into a spiral shape, and magnetic fluid 4 contained in the cylindrical air gap 5 of a cylindrical insulator 2 coheres along the shape of each spiral magnetic pole 21a-21f, so it is made into a spiral shape. And if the spiral cohesion of the magnetic fluid 4 occurs in order continually, the shape change of the magnetic fluid 4 which occurs at that time is that of the free surface 2b of the magnetic fluid similar to the shape of the rotation of a screw, and motive force can be obtained by driving water being inside the free surface 2b of the magnetic fluid in the same state as a screw pump.