In an output control device for a hydraulic pump of the variable displacement type wherein delivery pressure is led into a cylinder of the control device to move a control piston therein back and forth and let the piston change the inclination of a yoke, thereby varying the delivery of the pump, the improvement comprising a cam formed on a piston rod directly connected to the control piston, a hollow cylindrical sleeve slidable in the direction at right angles to the piston rod and adapted to remain in sliding contact with the cam so that, with the displacement of the control piston due to a rise of fluid pressure, the sleeve can be displaced by the cam away from the piston rod, said sleeve having a pressure pickup hole communicated with a fluid passage leading to the cylinder, a compensator piston slidably fitted in the sleeve and adapted to close the pressure pickup hole and shut off the flow of pressure fluid into the cylinder when the fluid pressure is zero and be moved, with the rise of fluid pressure, away from the pickup hole to open the same, and means for urging the compensator piston with a preset force into engagement with the piston rod, whereby the position of the pressure pickup hole is shifted according to the pump delivery so as to attain a desired pressure and control the pump output.