To improve the performance and durability by unifying an output shaft with an rotatable inclined plate, and controlling a spool type switching valve, which is radially arranged, with an eccentric shaft connected to the other end of the output shaft on the basis of a difference of angle against the input shaft, and unifying a cylinder block and a rotary port with a switching valve part so as to be assembled in the input shaft.

A cylinder block 21 is rotated at the same rotating speed with a second shaft 14, to which a mechanical rotating force is given. When a pipeline for supplying and returning oil pressure is connected to external connecting ports 81, 82, a cylinder port 22 is connected to any one of two concentrical circular ports 86, 87 by a spool type switching valve 23 which is stroked on the basis of a difference of rotating angle between an eccentric shaft 15, which is connected to a first shaft 13, and a cylinder block 21, which is connected to a second shaft 14, through an oil passage of a port block 83, two concentrical ports 86, 87 and a port of a cover block 27. As a result, a piston 30 is moved forward and backward with suction and discharge of the fluid, and a cam plate 51 is rotated so as to add the rotating speed of the cylinder block 21.