An impact tool which performs a predetermined operation on a workpiece by axial striking movement of a tool bit coupled to a front end region of a tool body , comprising: a motor that is housed in the tool body , a drive shaft that is disposed in parallel to an axial direction of the tool bit and adapted to be rotationally driven by the motor , a ring-like member that is rotatably mounted onto the drive shaft and caused to swing in the axial direction of the tool bit by rotation of the drive shaft , a tool driving mechanism that is connected to one end region of the ring-like member in a direction transverse to the axial direction of the tool bit and is caused to rectilinearly move in the axial direction of the tool bit by swinging movement of the ring-like member and thereby rectilinearly drives the tool bit , and a counter weight that is mounted movably in the axial direction of the tool bit and reduces vibration which is caused in the tool body in the axial direction of the tool bit during operation, wherein: the counter weight has a connecting part (157; 161, 163) that comes in contact with an outer edge part of the ring-like member in at least one of axial directions of the tool bit , and the counter weight is connected to the ring-like member via the connecting part (157; 161, 163), and characterised in that the connecting part comprises a protrusion protruding toward a center of a semicircular part of the counter weight , which semicircular part is disposed around a generally lower half region of the ring-like member , such that a side surface of the protrusion is opposed to at least one side of the outer edge part of the ring-like member . a motor that is housed in the tool body , a drive shaft that is disposed in parallel to an axial direction of the tool bit and adapted to be rotationally driven by the motor , a ring-like member that is rotatably mounted onto the drive shaft and caused to swing in the axial direction of the tool bit by rotation of the drive shaft , a tool driving mechanism that is connected to one end region of the ring-like member in a direction transverse to the axial direction of the tool bit and is caused to rectilinearly move in the axial direction of the tool bit by swinging movement of the ring-like member and thereby rectilinearly drives the tool bit , and a counter weight that is mounted movably in the axial direction of the tool bit and reduces vibration which is caused in the tool body in the axial direction of the tool bit during operation, wherein: the counter weight has a connecting part (157; 161, 163) that comes in contact with an outer edge part of the ring-like member in at least one of axial directions of the tool bit , and the counter weight is connected to the ring-like member via the connecting part (157; 161, 163), and characterised in that the connecting part comprises a protrusion protruding toward a center of a semicircular part of the counter weight , which semicircular part is disposed around a generally lower half region of the ring-like member , such that a side surface of the protrusion is opposed to at least one side of the outer edge part of the ring-like member . the counter weight has a connecting part (157; 161, 163) that comes in contact with an outer edge part of the ring-like member in at least one of axial directions of the tool bit , and the counter weight is connected to the ring-like member via the connecting part (157; 161, 163), and characterised in that the connecting part comprises a protrusion protruding toward a center of a semicircular part of the counter weight , which semicircular part is disposed around a generally lower half region of the ring-like member , such that a side surface of the protrusion is opposed to at least one side of the outer edge part of the ring-like member . <EOS>