A backpack work machine is provided and may include a backpack frame, a motor mounted on the backpack frame, a driven device driven by the motor, and an arm provided at a lower portion of the backpack frame. The arm is rotatable around an axis line that extends in a left-right direction of the backpack frame and has in a fore end portion thereof a throttle lever regulating output of the motor. The backpack frame also has in the lower portion thereof a support axis having an axis line, and the arm is supported by the support axis so as to be rotatable around the axis line of the support axis within a rotation range that extends between an up-down direction of the backpack frame and a front-rear direction of the backpack frame.