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 (50, 51) 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 (52, 53) are formed between both end portions (50, 51) 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 (50, 51) 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 (52, 53) are formed between both end portions (50, 51) 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 (50, 51) 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 (52, 53) are formed between both end portions (50, 51) 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 (52, 53) are formed between both end portions (50, 51) 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.