A clutch mechanism for a hydrostatic continuously variable transmission in which a high pressure oil path and a low pressure oil path are shortened to change-over a transmittance of power. A spring sheet is provided of which manufacturing and assembling are simple and the number of component parts is reduced. This clutch mechanism for a hydrostatic continuously variable transmission includes a cam plate member arranged at the end part of the transmission shaft, a roller engaged with the cam plate member and moved in a diametrical outward direction with a centrifugal force, a roller bearing member slid axially through an outward motion of the roller, a spring sheet member for biasing the roller bearing member toward the roller, and a spring sheet member for supporting the spring member. The spring sheet member is held by said cam plate member and said casing and is supported.