To provide a lubricating system for the swash-plate bearing of the HST-type transmission, which can lubricate efficiently the space between the cradle-type, movable swash-plate and the bearing face of the swash-plate, and has a simple lubricating setup.

The lubricating system is constituted of a cam 27 integrally formed with a trunnion arm 9, a piston 11 driven by the cam 27, which pressurize working oil in a oil path 20A, a spring 12 for returning the piston 11 to the original position and a check valve 15 for introducing working oil into the oil path 20A by a differential pressure between in and out of the oil path 20A. Or the lubricating system is constructed in such a way that a cam 25a is formed integrally with the movable tilt-plate 25, the piston 11 is mounted on a swash-plate bearing holder 20h or housing 20. The piston 11 pressurizes working oil in an oil path 20E with rotating action of the movable swash-plate 25 and the cam 25a. Manipulation of the swash-plate makes the cam 25a rotate, the cam 25a pressing the piston 11 to pressurize the oil path 20E, resulting in introduction of working oil into the bearing face of the swash-plate.