A working machine having a working part driven by an engine and a transporting part driven by an electric motor. The rotation of the electric motor is controlled by a control part. The speed of the engine as of when the working part is brought to a working state by a work on/off switch being turned on is taken as a reference speed, and a correction coefficient corresponding to this reference speed is taken as an upper limit value. A correction coefficient corresponding to the present speed of the engine is determined. A required acceleration set in correspondence with the size of the actual travel speed of the transporting part is multiplied by the determined correction coefficient to correct this required acceleration. The control part acceleration controls the rotation of the electric motor in accordance with the corrected required acceleration.