To provide a pressure oil supplying device capable of obtaining the high output necessary for various working mechanisms of a working vehicle and easily coping with the change of the output of an oil-hydraulic pump.

This pressure oil supplying device comprises an oil feed pump connected to an input shaft of the HST to be driven, and an oil passage plate mounted between the HST and the oil feed pump mountably and demountably supporting the oil feed pump, and the oil passage plate comprises an oil taking-in port opened on an outer face of the oil passage plate for taking the pressure oil discharged from the oil feed pump, a branching part for branching the taken pressure oil into at least two channels, a valve mechanism for adjusting the oil in one branched channel to the oil pressure for supplying the hydraulic oil, of the HST, an output port for supplying, opened on a HST mounting face for guiding the oil having passed through the valve mechanism to an oil supply port of the HST, and an output port for working, opened on an outer face of the oil passage plate for guiding the oil in the other branched channel to the working mechanism of the working vehicle.