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 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, the second rotation speed being greater than the first rotation speed; and a switching changing unit to change the first rotation speed or the second rotation speed 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 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, the second rotation speed being greater than the first rotation speed; and a switching changing unit to change the first rotation speed or the second rotation speed 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 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, the second rotation speed being greater than the first rotation speed; and a switching changing unit to change the first rotation speed or the second rotation speed 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 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, the second rotation speed being greater than the first rotation speed; and a switching changing unit to change the first rotation speed or the second rotation speed according to an operation amount of the work operation member.