A power working machine has a machine body, a drive source mounted on the machine body for driving a work implement connected to the machine body, and an operating handle mounted on the machine body for undergoing rotation relative to the machine body. A throttle lever is mounted on the operating handle for undergoing pivotal movement to adjust an output of the drive source. A lock mechanism is mounted on the operating handle for locking the operating handle at a preselected rotational angular position relative to the machine body. A lock cancellation lever is mounted on the operating handle for unlocking the lock mechanism to thereby permit rotational movement of the operating handle relative to the machine body. A stopper section is mounted on the operating handle for permitting operation of the lock mechanism while preventing pivotal movement of the throttle lever and for preventing operation of the lock mechanism while permitting pivotal movement of the throttle lever.