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 (180, 185) 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 (180, 185) 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 (180, 185) 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 (180, 185) 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 (180, 185) 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 (180, 185) 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 (180, 185) 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 (180, 185) 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 (180, 185) 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 (180, 185) 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.