A self-propelled work machine, in which the load of the work unit increases according to an increase in the travel speed. The self-propelled work machine includes electric motors for driving the travel units, an engine for driving the work unit, a work drive instruction unit for instructing the work unit to turn on, and a control unit for controlling the electric motors. The control unit reduces the actual speed of the electric motors by using PID control so that the actual rotational speed of the engine returns to a reference rotational speed when the actual rotational speed of the engine falls below the reference rotational speed in the state in which the work unit is turned on by the work drive instruction unit. The reference rotational speed is a reference value used when the work unit is driven by the engine.