A fastening tool, which uses a fastener including a bolt and a cylindrical hollow collar that is engageable with the bolt , the bolt having a head part integrally formed with a shaft part having a groove , to fasten a workpiece between the head part and the collar , the fastening tool comprising: a bolt-gripping part configured to grip an end region of the shaft part , an anvil configured to be engaged with the collar , the fastening tool being characterised in that it comprises a motor configured to drive and move the bolt-gripping part relative to the anvil in a specified longitudinal-axis direction, and a control part configured to control driving of the motor , wherein: the fastening tool is configured such that, when the bolt-gripping part grips the end region of the shaft part and moves relative to the anvil in a specified first direction of the longitudinal-axis direction, the anvil presses the collar fitted onto the shaft part in a second direction opposite to the first direction of the longitudinal-axis direction and inward in a radial direction of the collar , so that a hollow part of the collar is crimped to the groove while the workpiece is clamped between the collar and the head part , whereby swaging of the fastener is completed while the end region remains integrated with the shaft part , the control part completes swaging of the fastener by terminating a movement of the bolt-gripping part in the first direction relative to the anvil based on driving current of the motor , and the control part completes the swaging of the fastener further based on an amount of change in rotation speed of the motor . a bolt-gripping part configured to grip an end region of the shaft part , an anvil configured to be engaged with the collar , the fastening tool being characterised in that it comprises a motor configured to drive and move the bolt-gripping part relative to the anvil in a specified longitudinal-axis direction, and a control part configured to control driving of the motor , wherein: the fastening tool is configured such that, when the bolt-gripping part grips the end region of the shaft part and moves relative to the anvil in a specified first direction of the longitudinal-axis direction, the anvil presses the collar fitted onto the shaft part in a second direction opposite to the first direction of the longitudinal-axis direction and inward in a radial direction of the collar , so that a hollow part of the collar is crimped to the groove while the workpiece is clamped between the collar and the head part , whereby swaging of the fastener is completed while the end region remains integrated with the shaft part , the control part completes swaging of the fastener by terminating a movement of the bolt-gripping part in the first direction relative to the anvil based on driving current of the motor , and the control part completes the swaging of the fastener further based on an amount of change in rotation speed of the motor . the fastening tool is configured such that, when the bolt-gripping part grips the end region of the shaft part and moves relative to the anvil in a specified first direction of the longitudinal-axis direction, the anvil presses the collar fitted onto the shaft part in a second direction opposite to the first direction of the longitudinal-axis direction and inward in a radial direction of the collar , so that a hollow part of the collar is crimped to the groove while the workpiece is clamped between the collar and the head part , whereby swaging of the fastener is completed while the end region remains integrated with the shaft part , the control part completes swaging of the fastener by terminating a movement of the bolt-gripping part in the first direction relative to the anvil based on driving current of the motor , and the control part completes the swaging of the fastener further based on an amount of change in rotation speed of the motor . <EOS>