PURPOSE: To smooth angle control of the swash plate of a hydraulic continuously variable transmission.

CONSTITUTION: A swash plate 3 for operating a variable displacement pump 2 to be rotated together with an input shaft l in the direction along the input shaft 1 while guiding it is provided around the swash plate shaft 4 so as to be oscillated, and a ball 6 is interposed between a cam plate 5 capable of being rotatably operated around a core of the input shaft 1 and the swash plate, and the swash plate 3 is oscillated around the swash plate shaft 4, so as to operating-control the swash plate angle.