the present invention addresses the problem of being able to increase the effect of preventing an engine from stalling by reducing the engine load attributable to a fixed - capacity hydraulic pump . a working vehicle provided with a fixed - capacity hydraulic pump driven by power from an engine and a working hydraulic actuator driven by working oil pumped from the fixed - capacity hydraulic pump is a rotary working vehicle which is provided with a pressure modifying means for modifying the pressure of working oil from the fixed - capacity hydraulic pump , and the rotary working vehicle is such that if the actual number of revolutions of the engine is reduced by a set number of revolutions as the load on the engine increases , then the pressure modifying means operates in accordance with the deviation between the actual number of revolutions of the engine and the specified number of revolutions , and the pressure of the working oil from the fixed - capacity hydraulic pump is modified .