The present invention relates to an oil cooling apparatus for hydrostatic transmissions that includes a cooling main body coupled to a transmission case in which a hydrostatic transmission is installed; an accommodating groove formed in the cooling main body to accommodate oil; a cover unit coupled to the cooling main body to cover the accommodating groove; a supply port configured to supply the oil to the accommodating groove; a discharge port configured to discharge the oil from the accommodating groove; a plurality of guide ribs installed at positions spaced apart from each other to guide a flow direction of oil flowing along a flow path formed in the accommodating groove; a first hurdle unit coupled to at least one of the guide ribs to form a first flow region through which the oil passes; and a second hurdle unit coupled to at least one of the guide ribs to form a second flow region through which the oil passes.