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 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 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 . <EOS>