A working machine comprising: a machine body ; an engine provided on the machine body : a motor/generator to perform an assisting action in which the motor/generator functions as a motor to assist the engine in driving and an electricity generating action in which the motor/generator functions as a generator to generate electricity using power from the engine ; a working device configured to function using power from the engine and the motor/generator ; and a work operation member for operation of the working device ; the working machine being characterized in that it further comprises: an action control unit to cause the assisting action to be performed when a rotation speed of the engine is equal to or less than a first rotation speed (N1) and cause the electricity generating action to be performed when the rotation speed of the engine is equal to or greater than a second rotation speed (N2), the second rotation speed (N2) being greater than the first rotation speed (N1); and a switching changing unit to change the first rotation speed (N1) or the second rotation speed (N2) according to an operation amount of the work operation member . a machine body ; an engine provided on the machine body : a motor/generator to perform an assisting action in which the motor/generator functions as a motor to assist the engine in driving and an electricity generating action in which the motor/generator functions as a generator to generate electricity using power from the engine ; a working device configured to function using power from the engine and the motor/generator ; and a work operation member for operation of the working device ; the working machine being characterized in that it further comprises: an action control unit to cause the assisting action to be performed when a rotation speed of the engine is equal to or less than a first rotation speed (N1) and cause the electricity generating action to be performed when the rotation speed of the engine is equal to or greater than a second rotation speed (N2), the second rotation speed (N2) being greater than the first rotation speed (N1); and a switching changing unit to change the first rotation speed (N1) or the second rotation speed (N2) according to an operation amount of the work operation member . a motor/generator to perform an assisting action in which the motor/generator functions as a motor to assist the engine in driving and an electricity generating action in which the motor/generator functions as a generator to generate electricity using power from the engine ; a working device configured to function using power from the engine and the motor/generator ; and a work operation member for operation of the working device ; the working machine being characterized in that it further comprises: an action control unit to cause the assisting action to be performed when a rotation speed of the engine is equal to or less than a first rotation speed (N1) and cause the electricity generating action to be performed when the rotation speed of the engine is equal to or greater than a second rotation speed (N2), the second rotation speed (N2) being greater than the first rotation speed (N1); and a switching changing unit to change the first rotation speed (N1) or the second rotation speed (N2) according to an operation amount of the work operation member . an action control unit to cause the assisting action to be performed when a rotation speed of the engine is equal to or less than a first rotation speed (N1) and cause the electricity generating action to be performed when the rotation speed of the engine is equal to or greater than a second rotation speed (N2), the second rotation speed (N2) being greater than the first rotation speed (N1); and a switching changing unit to change the first rotation speed (N1) or the second rotation speed (N2) according to an operation amount of the work operation member . <EOS>