An ascender comprising: a pulley capable of removably winding a rope thereon; an input shaft capable of removably connecting an output shaft of a rotary electric tool thereto; a support member that supports the pulley and the input shaft to be rotatable and that includes an open part which enables the rope to be wound on the pulley; a transmission mechanism interposed between the input shaft and the pulley so as to transmit a rotational force of the input shaft to the pulley; a rope guide (31,32, 33, 34) provided on the support member so as to guide the rope wound on the pulley at an entrance passage and an exit passage of the rope and a closing member that is movable for opening and closing the open part, the closing member being pivotally supported on a support shaft including a carabiner hanging hole and mounted on the support member; characterised in that the ascender further comprises: a cam pivotally supported on the support member so as to be movable toward and away from the pulley, the cam being configured to move toward the pulley to bite into the rope wound on the pulley to thereby prevent a movement of the rope when the rope is going to move in a descending direction, and to move away from the pulley to allow the movement of the rope when the rope is going to move in an ascending direction; an energizing member that energizes the cam in a direction to move toward the pulley; an operating member for an action to move the cam away from the pulley. a pulley capable of removably winding a rope thereon; an input shaft capable of removably connecting an output shaft of a rotary electric tool thereto; a support member that supports the pulley and the input shaft to be rotatable and that includes an open part which enables the rope to be wound on the pulley; a transmission mechanism interposed between the input shaft and the pulley so as to transmit a rotational force of the input shaft to the pulley; a rope guide (31,32, 33, 34) provided on the support member so as to guide the rope wound on the pulley at an entrance passage and an exit passage of the rope and a closing member that is movable for opening and closing the open part, the closing member being pivotally supported on a support shaft including a carabiner hanging hole and mounted on the support member; characterised in that the ascender further comprises: a cam pivotally supported on the support member so as to be movable toward and away from the pulley, the cam being configured to move toward the pulley to bite into the rope wound on the pulley to thereby prevent a movement of the rope when the rope is going to move in a descending direction, and to move away from the pulley to allow the movement of the rope when the rope is going to move in an ascending direction; an energizing member that energizes the cam in a direction to move toward the pulley; an operating member for an action to move the cam away from the pulley. a cam pivotally supported on the support member so as to be movable toward and away from the pulley, the cam being configured to move toward the pulley to bite into the rope wound on the pulley to thereby prevent a movement of the rope when the rope is going to move in a descending direction, and to move away from the pulley to allow the movement of the rope when the rope is going to move in an ascending direction; an energizing member that energizes the cam in a direction to move toward the pulley; an operating member for an action to move the cam away from the pulley.