A hydrostatic transaxle apparatus comprises a housing in which an HST, a pair of axles, a differential unit differentially connecting the axles to each other, and a horizontal counter shaft interposed between the HST and the differential unit. The HST comprises axial piston type hydraulic pump and motor mounted on vertically opposite surfaces of a center section, respectively, so as to be fluidly connected to each other so that pump and motor shafts are disposed vertically coaxially to each other. The center section is disposed adjacently to the differential unit and one of the axles. A cooling fan is fixed on the pump shaft projecting outward from the housing. When along the pump shaft, most of the housing except portions thereof for housing the respective axles is disposed within an area of rotary locus of the cooling fan.