An impact fastening tool for converting a rotary force of a rotary drive source into intermittent impacts by an impact generation mechanism , and fastening a screw by a rotary force of a main shaft applied by the impact force, the impact fastening tool comprising: a housing ; a slip ring portion ; and a torque detection means that detects a tightening torque, wherein: the slip ring portion includes a rotating electrode that rotates integrally with the main shaft , and a fixed connector that is in contact with the rotating electrode ; both end portions of the fixed connector are fixed; and a signal required for the torque detection means is transmitted through the slip ring portion ; characterized in that : at least two protrusion portions are formed between both end portions of the fixed connector ; the rotating electrode is disposed between one protrusion portion and the other protrusion portion such that the rotating electrode contacts the fixed connector at two or more points or in a line form; a part between the top of one protrusion portion and the top of the other protrusion portion is a valley portion ; a curvature of the valley portion is smaller than a curvature of the rotating electrode ; and two contact points are formed between the rotating electrode and the fixed connector . a housing ; a slip ring portion ; and a torque detection means that detects a tightening torque, wherein: the slip ring portion includes a rotating electrode that rotates integrally with the main shaft , and a fixed connector that is in contact with the rotating electrode ; both end portions of the fixed connector are fixed; and a signal required for the torque detection means is transmitted through the slip ring portion ; characterized in that : at least two protrusion portions are formed between both end portions of the fixed connector ; the rotating electrode is disposed between one protrusion portion and the other protrusion portion such that the rotating electrode contacts the fixed connector at two or more points or in a line form; a part between the top of one protrusion portion and the top of the other protrusion portion is a valley portion ; a curvature of the valley portion is smaller than a curvature of the rotating electrode ; and two contact points are formed between the rotating electrode and the fixed connector . the slip ring portion includes a rotating electrode that rotates integrally with the main shaft , and a fixed connector that is in contact with the rotating electrode ; both end portions of the fixed connector are fixed; and a signal required for the torque detection means is transmitted through the slip ring portion ; characterized in that : at least two protrusion portions are formed between both end portions of the fixed connector ; the rotating electrode is disposed between one protrusion portion and the other protrusion portion such that the rotating electrode contacts the fixed connector at two or more points or in a line form; a part between the top of one protrusion portion and the top of the other protrusion portion is a valley portion ; a curvature of the valley portion is smaller than a curvature of the rotating electrode ; and two contact points are formed between the rotating electrode and the fixed connector . at least two protrusion portions are formed between both end portions of the fixed connector ; the rotating electrode is disposed between one protrusion portion and the other protrusion portion such that the rotating electrode contacts the fixed connector at two or more points or in a line form; a part between the top of one protrusion portion and the top of the other protrusion portion is a valley portion ; a curvature of the valley portion is smaller than a curvature of the rotating electrode ; and two contact points are formed between the rotating electrode and the fixed connector . <EOS>