A control device for a work machine hydraulic pump used on a work vehicle according to the present invention has an object to rapidly accelerate the engine to start the vehicle quickly and to rapidly produce a large tractive force when an operator starts depressing the accelerator pedal while operating the work machine operating lever from the neutral position. The control device controls the capacity of the work machine hydraulic pump so as not to exceed the capacity upper limit corresponding to the currently detected engine speed, when the engine speed detected by the engine speed detecting device is equal to or lower than a predetermined speed (maximum torque speed).