To suppress temperature increase of a working fluid in a closed hydraulic circuit by efficiently cooling a cylinder block only by adding simple configuration, in a hydrostatic continuously variable transmission including a cylinder block for a hydraulic pump and a cylinder block for a hydraulic motor comprised of one cylinder block.

A cylinder block cooling structure includes: an oil guide passage 22 which guides oil from an oil passage 7 in an input shaft 1 to the vicinity of a side face of a cylinder block 8; an oil receiving plate 23 provided on the side face of the cylinder block for receiving the oil guided from the oil guide passage and supplied to a centrifugal side by a centrifugal force; and a cylinder block cooling oil passage 24 formed in the cylinder block from an oil introducing hole 28 formed on the side face of the cylinder block to introduce the oil received by the oil receiving plate, to an oil discharge hole 29 formed in the outer circumference of the cylinder block.